Art. LXIV.—Milk as a Vehicle of Disease.
[Read before the Auckland Institute, 27th October, 1890.]
The present age is remarkable for the interest taken by the general public in the public health. From times immemorial it has been regarded as the duty of governing authorities to protect the communities under their care from such forces as might occasion disease and death. Indeed, the cities of Greece and Rome in the days of their ancient splendour might in many ways compare favourably with modern towns as regards their sanitary arrangements.
With the advance of civilization it has been found necessary to cope with new enemies to health. For example, as villages have become towns vast systems of drainage have been demanded, and with the influx of population into manufacturing centres, and the resulting overcrowding, legislation has had to be provided regulating the arrangement of buildings designed for the accommodation of the poorer working classes.
There is, however, another direction in which it has been necessary to advance with the times. Science, ever searching for explanations of facts, has been able to point out causes of prevalent disease—causes previously unsuspected, or, if suspected, not proved. A recognition of the fact that typhus fever required for its propagation the poisoned air and squalid surroundings once so frequent in the alleys and closes of the larger cities of Britain was followed by legislation which so vastly improved the homes and surroundings of the poorest working-classes that typhus is now almost unkown where it was once rampant. With increased knowledge also of the conditions favouring the development of typhoid fever, even it, still a scourge in almost every country, is gradually being overcome, and its ravages decreased.
The progress of sanitary science and the consequent advance in the direction of preventive medicine has been especially marked during the last twenty or thirty years, and probably what is popularly known as the “germ theory” has had the greatest influence in effecting this. At present especial interest is being taken by those concerned in preserving the public health in the consideration of the influence which our animal food has in propagating disease. That it is at present a means of spreading disease there is no doubt. Most interest is shown probably in the question as to whether the bodies of animals affected by certain diseases are fit for
food; but closely allied to this subject, and I believe of even greater importance, is that which more especially concerns us to-night—“The extent to which milk may serve as a vehicle of disease.”
The importance of the matter cannot be understood unless we have a fair idea of the part which milk plays as an article of human food, and it may be well for us to turn our attention to this for a few minutes.
Milk has been called by an author famous as an authority on the subject of diet a complete and perfect food. It contains all those elements which are constituents of a sufficient and healthy food for man. These elements are—(1) Substances containing nitrogen; (2) carbohydrates, a name given to a class of chemical bodies in which are the starches and sugars; (3) fats; (4) mineral salts.
Children and adults usually take what is called a mixed diet, some parts of their food (such as meat) containing mostly nitrogenous matter; potatoes are chiefly starch; butter is nearly all fat. Their different foods are taken in no fixed proportions, but as taste or opportunity may direct—more of one and less of another. Although, however, one may put into one's mouth very indefinite quantities of each element of food, one's digestive apparatus has only limited capabilities for the digestion of each of them, and only a limited amount of the whole food is really digested. The remainder simply goes to waste, and is eliminated.
The stomachs of all individuals are not equally strong—i.e., they have not equal powers of digestion—and in the extremes of life (both in infancy and in old age) the digestive powers are comparatively weak. The same Providence which endues an infant with a weak stomach provides for it in milk a food in which the fats, the matter containing nitrogen, the sugar, and the salts are mixed in the quantities and form best for their easy digestion.
All milks are not exactly alike as to the proportion of their various ingredients. What will suit a foal is not the best for a lamb, nor, as a rule, is the milk of a cow so good for a human infant as that from its own mother's breast. Still, in cases where a mother may not or will not nurse her own offspring, and a good wet-nurse is not procurable, the best substitute for the child's natural food is undoubtedly milk from some other animal. Among most European nations the cow is the chosen animal, but the goat, ewe, mare, and reindeer are used in some districts.
Not only, however, to infants is it an advantage to have a good supply of milk—as we have seen, a complete food in a form easy for digestion; for the old and the invalid it is times invaluable, and for the rest of mankind, especially for the
children, the experience of centuries has proved its worth. Its value compared with that of other common foods can be appreciated by any one acquainted with the difference in strength and appearance between children reared where a supply of milk is abundant and those whose stomachs are constantly oppressed by the heavy work of trying to digest bacon and other cheap meats, which, washed down by copious libations of tea, form the staple food of the poor in many large towns in Britain. Even in country districts not far distant from our own town, settlers do not see the advantage of a good supply of milk for their children, and the pale dyspeptic countenances of the young folks are the reward of a diet arranged by the ignorance, carelessness, or laziness of their parents.
The milk of domestic animals has from remote ages been generally used by civilized peoples, but there is at the present time an increased recognition of its value as a food, and a growing demand for it. The extension of railways and other facilities for its speedy conveyance to centres of population have enabled an increasing demand to be satisfied; and enactments against adulteration have given confidence to consumers and protection to honest farmers and dairymen. It has been estimated that in England there is a daily consumption of such an amount of fresh milk as would, if equally divided amongst the whole population, allow one-fifth of a pint to each individual in the country; and this amount, great as it is, represents only one-third of the total milk-consumption: the remainder is made into butter and cheese and other manufactured articles of food. The fact of such an enormous consumption of milk is sufficient to suggest the greatly injurious influence the milk-supply may have on the health of the nation unless adequate precautions are taken to insure that a pure article is supplied—milk neither adulterated nor containing in it the germs of disease.
That much preventible sickness is due to the use of a bad quality of milk is certain, and it may also be regarded as decided that milk may be the means of transmitting diseases of a specific nature, such as the fevers, typhoid, scarlatina, measles, and diphtheria; also tuberculosis or consumption, and possibly leprosy.
For convenience we may consider diseases caused by means of milk under two heads—(1) Derangements of digestion due to a bad quality of milk consumed; (2) specific infectious diseases.
We will first deal shortly with the derangements of digestion which occur chiefly in children under two years of age. These digestive troubles may follow the use of milk from cows fed upon some food which, passing into their milk, renders it more difficult of digestion, or itself exerts a directly harmful
influence on the child; or they ensue from the use of milk from cows themselves in a bad state of health. But the usual fault on the part of the milk causing digestive disturbance is that it has become fermented—it has been exposed to the influence of germs which have set up a fermentative process, the products of which are irritating to the stomach and bowels.
If milk is kept from the action of germs it remains good, and, although germs must enter it if exposed to the air, still the probability of a sufficient number of germs of the kinds necessary to cause harmful fermentation, getting access to it, is much lessened if only cleanliness is observed in connection with the operations of milking, distributing, and storing the milk.
The surroundings of a milking-shed of the ordinary type are by no means fitted to insure cleanliness. The cows usually, at any rate in winter-time, have to splash through mud and filth to reach the shed. The milking is done by hands not over-clean, and without cleansing the teats. The buckets in which the milk is first placed are cleansed by being rinsed in water the purity of which would not stand the test required to establish it as fit for drinking by man; the same with regard to the cleansing of the cans in which the milk is conveyed to the consumers. These cans, too, are often not dust-proof, which is a by no means unimportant essential in a place where, as in Auckland, so little attention is paid to the thorough laying of the dust which rises from the filth of the streets. Even when milk has reached the consumer's house it has yet to run the risk of exposure to dust in vessels probably themselves imperfectly cleaned; the wonder, indeed, is that so little milk is actually spoiled by becoming soured.
Sourness, however, is not a test as to whether milk is harmful or not. The germ which causes ordinary sourness of milk is not particularly harmful; but usually associated with it are others with a more noxious influence. These, indeed, may be present although the milk remains quite sweet.
The ills resulting in children from the use of fermented milk are to be avoided, in the first place, by having the utmost care for cleanliness—by seeing that the teats of the cow, the hands of the milker, all cans and other utensils through which the milk may pass, are thoroughly and well cleaned. All water used for the purpose should be such as is fit for man to drink. It is strange that folk most fastidious as to the water that passes their lips should yet wash their milkcans in water from a source into which, perhaps, the drainage of the stockyard passes. I have seen such a state of things on more than one occasion. In first-class dairies in Britain it is usual not only to rinse the cans with cold water, but, in addition
to cleanse them with steam. Cans for the conveyance of milk should be dust-proof, and so, too, the vessels in which the milk is kept after reaching the house of the consumer. The finding at the bottom of a glass of milk small pieces of hay and other dirt usually leads to the imputation of a want of cleanliness on the part of the dairyman, while in reality these impurities often proceed from street-dust, which, in fact, consists largely of manure. The blame should be laid on the city authorities who allow such a dust nuisance to prevail.
Where a consumer is in doubt regarding the condition of the milk it should be boiled before use. This proceeding destroys not only the germs causing ordinary fermentation, but also those which are the cause of the infectious diseases to which presently I will more especially refer. It is doubtful if boiling in any way impairs the digestibility of milk.
The process of boiling, as it destroys germs and thus effectually prevents their multiplication, is said to be a process of sterilization—milk when boiled is said to be sterilized. It has been proposed, and in some places actually accomplished, to place sterilized milk in the market. In St. Petersburg, in the Children's Hospital, also in some large dairies and private families, the milk is heated in flasks to boiling-point, and hermetically sealed while in a state of ebullition. A similar process has been carried out on a smaller scale in Norway and in London.
In Copenhagen milk for children is sold by the druggists. All cows from which the milk proceeds are specially chosen, and subjected regularly to examination by veterinary surgeons. The cows are specially fed, and special precautions are taken to preserve the purity and freshness of the milk, which is placed in sealed bottles before being sent to the druggists, by whom families are supplied.
It is clear from what I have said that the prevention of harm to children through their being supplied with unwholesome milk lies to a very great extent in the hands of consumers. They must themselves see that they take precautions to exclude dust from the milk, to cleanse thoroughly all vessels in which milk is placed, and should insist on being supplied with milk free from dirt, and otherwise, so far as they are capable of judging, entirely sound. Such insistence will compel the dairyman and dairy-farmer for the sake of their trade to regulate to some extent the sanitary arrangements of their premises and the methods in which the milking and the distribution are carried out. Is this sufficient? It has been decided in most civilized countries that something further is required—that the public authorities should have some control over the milk-supply. Through ignorance or
carelessness, or through temptation or gain, suppliers are liable, in spite of all care on the part of consumers, to supply unwholesome milk. We have seen that unwholesome milk does not necessarily give signs of its unwholesomeness prior to its consumption, and in such cases the consumer is at the mercy of his milkman. It is necessary for cowsheds, dairies, and other buildings connected with the trade to be open for inspection to an authorized official competent to detect such arrangements as may be prejudicial to the wholesomeness of the milk. Such supervision is, however, required much less on account of the liability of children to be affected by digestive derangements from the use of unsound milk than because of another great danger to which we have hitherto only incidentally referred—the danger of milk being a means of carrying infectious disease. Milk serving such a purpose may give no sign that it is in any way impure. It is only after an epidemic shows itself that a chain of evidence is put together proving that the milk-supply is at fault. Then it is found that with proper precautions the epidemic might have been prevented.
For instance, scarlet fever breaks out in some neighbourhood; there is a simultaneous outbreak in several families, and in the different families one, two, or more are affected at the first appearance of the disease. The children from the several infected houses have never come in contact with each other nor with any known to be suffering from scarlet fever; but it is noticed that all the families are supplied with milk from the same dairy, and that those first affected have all partaken of milk supplied during one or two special days. Others in the same families using milk from another dairy, or absent from home on these special days, have all escaped—at any rate, in the first instance. Attention being directed to the dairy from which the milk is derived, it is found that there is an explanation of the way in which the milk may have become infected. Very frequently one of the milkers has children suffering from scarlet fever, or has himself shown symptoms, but so mild as not to compel him to give up his work. Families supplied from the same dairy, but with milk kept apart from that in which the affected individual has been concerned, have all kept free of the disease. The evidence that the milk was a cause of the epidemic is conclusive, but only after it is too late to prevent the mischief. In such a case the consumer has no opportunity whatever of preventing his family from participating in the infection, and so we find in all cases of epidemics arising from the milk-supply. A guarantee of prevention lies only in the taking of such measures as will abolish all possible source of infection from the time the milk leaves the cow until it is delivered to the consumer. The interest of the community in preventing epidemics of infectious
disease is such as to warrant the adoption of the strictest regulations necessary to insure a pure milk-supply. Of course, all cases of infectious disease do not originate in the milk-supply—probably only a small proportion of them; but the repression is urgently required of any factor in maintaining such a death-rate from infectious disease as at present prevails. The deaths from such diseases do not form the whole of their evil results: the temporary illness and suffering of those that recover and the permanent injury done to numbers of them must also be taken into account.
Infectious diseases, it must now be allowed, are probably all due to specific germs. Some of them have been absolutely proved due to the presence of a special kind of germ in the body. The evidence in the cases of the other fevers, so far as it goes, makes the theory very probably true as regards them. One kind of germ causes one special fever and no other. The germ of scarlet fever is quite distinct from that causing typhoid or any other infectious disease. This is what is meant by saying that each infectious disease is due to a specific germ.
In order for a man to be infected with any infectious fever the specific germ of that fever must be introduced into his system; and when milk is the vehicle of infection the milk the individual takes must contain the specific germ. Now, many germs placed in milk find in it all that they require to thrive and propagate their kind. Just as in good ground weeds thrive and multiply because they are in circumstances favourable for their nourishment and growth, so germs find in milk a first-class soil, and multiply at an amazing rate. In a few hours from the introduction of a germ or two the whole of the milk is swarming with them. We can thus understand how one or two specific germs finding access to a large quantity of milk are able to cause disease in many individuals. The fact that in many dairies the milk from all the cows is mixed, and that in milk-shops the milk from different farms is not always kept distinct, adds to the danger of spreading disease. Of course, when milk from different sources is mixed, the infecting germs, if present in only one of the mixed lots, are not so abundant in the same quantity of milk immediately after mixing, but the whole being now infected the germs may go on multiplying in it. To cause disease, however, it is not necessary for a large number of the disease-causing germs to be swallowed, for one or two getting access to the body are capable of soon becoming many under certain circumstances. They multiply within the body.
The principal infectious diseases, epidemics of which have been traced to originate in the milk-supply, are typhoid fever, scarlet fever, and diphtheria.
Typhoid, or enteric, or gastric, or low fever is the most common of the specific fevers, and is endemic in almost every quarter of the globe. It is probably caused by a germ which was discovered and described some eight years ago. This germ is present in the excreta of those suffering from typhoid fever, and most cases of infection are caused directly or indirectly from the excreta of typhoid patients contaminating water, food, or perhaps the air. It must be well known to all here how frequently the prevalence of typhoid fever is ascribed to defective drainage. When drainage is defective the waste material from houses is not properly removed. It lodges in some depression in the ground, or perhaps saturates the ground. At any rate, there is an accumulation of organic matter with plenty of moisture, just the condition necessary for the thriving of germs. Should the typhoid germ find access to this accumulation, in time the collection of filth becomes a very successful typhoid-breeding establishment. Soakage from this filth finds its way to some well, which is thus polluted and infected. Or dry weather comes; some of the filth dries up, is powdered, and is blown hither and thither into wells, tanks, food, or, it may be, directly into the nose or mouth of some one. The germs are not killed by being dried up; they are only for the time being prevented from multiplying. So soon as they become moist they again begin to develope. Milk is usually infected with the typhoid germs from an impure water-supply; possibly it is diluted with impure water, or polluted water is used to wash the cans and other dairy-utensils. In either case the germ is added to the milk. It may be that dust containing the typhoid germ reaches the milk. Hence one great necessity for placing milk in dustproof cans during its distribution. In Auckland the night-soil carts (containing excreta from typhoid folk as well as healthy) are very capable of distributing filth along the streets they traverse, and, as we know, the street-dust is not the least of the nuisances existing in the town.
Some assert that milk may become capable of conveying typhoid fever through water polluted with the typhoid poison being given to the cows. This theory, however, is not proved. Were this the case the system of the cow must be first infected, and evidence sufficient to prove that this is possible has not yet been brought forward.
As examples of the evidence often found connecting a typhoid epidemic with milk from a special dairy, let me mention one or two cases which have actually occurred.
In February, 1889, some fifty cases of typhoid fever occurred in Stirling and its neighbourhood, and were traced to be caused by milk from one farm. It was found that a case of fever had occurred at the farm-house, and the excreta were
disposed of by the watercloset, the soil-pipe from which went into a badly-jointed drain passing close to the milk-house. It seemed as if the milk became contaminated in consequence of the proximity of the defective drain to the milk-house, for families supplied direct from the milk-sheds escaped infection, and all families where infection did occur were supplied with milk which had been kept over night in the milk-house.
In Leeds, in 1873, an outbreak of typhoid fever was traced to the milk-supply from a special dairy. It was found that the dairyman had been ill with typhoid fever, that the excreta had been cast partly into a privy and partly on to a dunghill, and that drainage from each of these found its way into a well used both for domestic and for dairy purposes. The sudden outbreak of fever among families supplied from this dairy corresponded with the time necessary for the development of the fever after the first pollution of the well; and the cessation of the epidemic corresponded also with an interval after its being closed, consistent with the theory that its water had been infected.
Scarlet fever, like typhoid, is most probably due to a germ, but, unfortunately, in its case it is not decided on which germ the responsibility of such a scourge is to be cast. A London scientist, Dr. Klein, has discovered one germ which he regards as certainly the specific germ of scarlet fever. In Edinburgh, Dr. Edington has equally convinced himself and others that scarlet fever is not caused by Klein's germ, but by one quite different, which he himself has discovered. Till this question is settled we must be content to know that general evidence is in favour of some germ or other being at the root of the mischief known as scarlet fever. Granting that this specific germ does exist, it is present especially in the scales given off from the skin of scarlet-fever patients during convalescence, as well as during the more acute stage of the disease. In these scales the germs are blown about until perhaps they find a resting-place in the alimentary tract or air-passages of some other unfortunate individual, who thus becomes infected. It is, however, not only by the scales from the skin that the infection is carried, but probably by other excretions of the body. Scarlet fever is one of the most infectious of diseases, and to expose milk to the air in the immediate vicinity of a scarlet-fever patient, to allow any one recovering from the disease to partake in the duties of the dairy, or even any one who comes in contact with such a patient, is to court the risk of an epidemic. That scarlet fever has occasionally been conveyed to man through the agency of milk has been known for some fifteen or sixteen years. It was for long taken for granted that the milk became contaminated directly from a human source, but in 1886 a new question was raised with
regard to the contamination of milk with the poison of scarlet fever. It was suggested that cows suffered from the disease as well as man, and that an epidemic might arise from the use of milk from cows affected with it. The question was raised in consequence of a limited epidemic of the fever occurring in London, evidently due to the supply of milk from a certain farm at Hendon. It was proved that the milk must have been infected before it left the farm. It seemed, however, for a long time that the infection could not have come directly from a human source, and, as certain cows introduced into the dairy about that time were suffering from a feverish disease, investigations were set on foot to see if scarlet fever and this feverish disease in the cows were not identical. Dr. Klein, whom I have before mentioned, made experiments, and found apparently the same germ in both scarlet-fever patients and the diseased cows; and, according to him, this germ, whether obtained from a scarlet-fever patient or from a cow, when inoculated into calves, produced in them, with only slight differences, the original cow fever. This seemed conclusive, but later investigations threw some doubts on the results of Klein's research. Another outbreak of the same cow fever occurred at Hendon and elsewhere in 1887-88, but was accompanied by no outbreak of scarlet fever, although the milk of the diseased cows was sold and used. The animals which had originally brought the cow fever to Hendon came from Derbyshire, and it was ascertained that other cows from the same district sold at the same time had developed the same disease; but, although their milk had also been sold, no epidemic of scarlet fever had resulted. Finally it was shown that after all there was a possible source of infection of the milk through human agency. During one or two other epidemics of scarlet fever it was found that there was a feverish disease prevalent among cows in the neighbourhood, but this would appear to have been a mere coincidence. It has not been satisfactorily proved that scarlet fever does attack the cow, but it is very certain that it can readily be spread by the agency of a milk-supply. The same is probably true with regard to measles; but I can find no notices of epidemics of measles which have been traced to this source.
Diphtheria epidemics traced to the milk-supply have always been associated with an impure supply of water from the dairy in which the epidemic originated. In 1879 an epidemic at Leatherhead, in Surrey, affected thirty families almost simultaneously, and twenty-nine of these families had a supply from one dairy-farm. The water in use at this dairy came from a tank, and was decidedly impure from the presence of decaying organic matter. It was probably the means by which the milk became contaminated.
In speaking of scarlet fever, I have mentioned that it has been suggested that it affects the cow as well as man. The same has been suggested regarding diphtheria.
There are some acute cattle-diseases which, if not actually conveyable to man, at any rate cause the milk of cows affected with them to be unfit for human consumption. Such are the cattle plague, foot-and-mouth disease, and pleuro-pneumonia. The use of milk from cows suffering from these diseases may induce in man inflammation of the lungs of a severe and often fatal kind.
I now pass to another class of infectious disease affecting man which may be conveyed to him by means of milk. Those diseases of which I have hitherto been speaking are acute fevers in which the characteristic symptoms appear in a comparatively short time after infection, and in regard to which it is therefore a comparatively easy task to set on foot investigations to prove their possible connection with a milk-supply. Those diseases to which we now turn our attention are, as a rule, of a more chronic nature. Their symptoms are at first vague. Often it is not until months, even years, after they have been acquired that it is realised that the affected individual is suffering from them. To this class of diseases belong leprosy and tuberculosis.
With regard to leprosy and its connection with the milk supply, I would mention merely as a matter of interest a suggestion made by Dr. Neve, a medical missionary stationed at Kashmir, a man whose academic career proved him a careful and reliant observer. Dr. Neve says that in Kashmir leprosy exists to a considerable extent among herdsmen, all of whom also consume largely milk and milk-products. One adult may eat from 6lb. to 12lb. of curds in twenty-four hours; putrid buttermilk is considered a delicacy. It is easy to see that a leprous milkman might spread infection, and in this connection Dr. Neve points out that Europeans who drink unboiled milk, if they chance to live in a district where leprosy is endemic, might thus contract the disease. In fact, he says, this may be the explanation of various recorded cases. So much for leprosy.
The subject of tuberculosis demands much more attention. Perhaps I ought in the first place to state for the benefit of some what is meant by tuberculosis. It is the scientific name for what is more generally known as consumption—that fell disease the cause of which has until quite recently been so imperfectly known, and the ravages of which have for ages been so vast among civilized peoples, seeking its victims too especially among those who should be entering on their life's work in all their vigour. It is estimated that from 10 to 14 per cent. of all deaths are due to tuberculosis. In Britain,
150,000 deaths are annually registered as due to it. In Paris, about 20 per cent. of all deaths result from it; in Vienna, 15 per cent. of all deaths, but in some quarters of the town no less than 90 per cent. In New Zealand, during 1888, the death-rate from tubercular disease was rather more than 11 per cent.
I mention these figures to give some idea of the magnitude of the evil; but the deaths represent only a part. We must take into consideration the suffering which precedes death, and the loss to the community from the impairment of the usefulness of the sufferers, and from the necessity of others being engaged in nursing and attending to their wants.
The popular idea regarding consumption is, I think, that of a wasting disease in which the lungs especially are affected. It is now known that other organs of the body become diseased from the same cause—a specific germ, the Bacillus tuberculosis, this name being applied to it because its presence and development in any part of the body gives rise after a time to the formation of little diseased masses known technically as tubercles.
There is no doubt that certain individuals and certain families are much more prone to consumption than others, but it would appear that it is necessary that in every case the specific germ should find its way into the body of the person affected. When once it has entered the body, should it be deposited in any part the vital power of which is lowered by disease, by heredity, or other cause, in that part of the body it is especially liable to develope and then spread to other parts of the body. How then, we may inquire, does the germ get into the system ? Experiment and research show that it may enter the body either through the air-passages or through the alimentary tract (the stomach and bowels). It is with the latter that we have to concern ourselves to-night in considering what part milk may play in the spread of tuberculosis.
Among other facts which establish the view that the germ of tuberculosis may enter the system through the alimentary tract I may mention the following: A consumptive patient, being recommended to live in the country, went to a farm-house at which a considerable number of poultry were kept. The spittoon used by him being emptied in the farm-yard, the fowls were in the habit of devouring the expectoration. After a few weeks an epidemic of consumption broke out among the poultry, causing a mortality of about fifty in three or four months.
Experiments conducted with a view to confirm the suspicion that food could convey tuberculosis have given a positive
result. Guinea-pigs and rabbits fed constantly on food containing tubercle germs in time developed the disease, and the examination of their bodies showed that the germ evidently entered the system through the walls of the bowels and thence invaded the rest of the body.
While tuberculosis most frequently affects the lungs in young adults, it is found that in young children it is especially the bowels and the adjacent parts that are affected. The examination of the bodies of children thus dying points out conclusively that the germs have entered the body through the walls of the bowels and spread thence. Such disease in children is especially frequent between the first and sixth years of life, and forms one of the most common causes of death during this period. The difference of the localities in the body which tuberculosis especially affects in adults and in children is explained by the fact that during early childhood the digestive system is especially taxed. The rapid growth of the body causes a demand for a large amount of digested matter to supply material for building up the tissues, and this demand throws so heavy a strain on the digestive organs that they are especially liable to be thrown out of order and rendered less capable of resisting disease.
It being probable that the germ of tuberculosis is able to make its inroads on the human frame by way of the alimentary tract, introduced in the first place with the food, it will be readily perceived how important it became to find out in what form of food the germ is liable to be present. Many facts pointed to the probability of animal food being an agent of infection—in fact, that a vast unknown accidental infection by this means had been going on for ages.
In cattle a disease exists known as bovine tuberculosis, unfortunately at the present time on the increase, and affecting especially the best breeds of dairy-cattle. This disease has during the last few years been shown to be due to the very same cause as the similar disease which plays such havoc with the lives of men, and it exists to such an extent and under such circumstances as to leave little doubt that much of the tuberculosis in man is due to infection through the use of meat or milk from tuberculous cattle. In 1881 the authorities of the Grand Duchy of Baden issued a report which applied to fifty-two towns, and which showed that where tuberculosis was prevalent among cattle it was equally prevalent among the human population, and was more prevalent in those parts of a town where the butchers paid least attention to the quality of the meat sold. Sir Lyon Playfair has recently in a debate in the British House of Commons pointed out that it is a significant fact that where tuberculosis in cattle increases there also consumption in its different forms increases, but
especially that form which attacks the digestive organs of children.
Professor Bang, of Copenhagen, by giving milk from tuberculous cows to pigs and rabbits has caused tuberculosis in them. Cream and buttermilk and butter made from the same milk showed the same infectivity.
An unintentional experiment was made in the following instance: A herd of valuable cows was found to contain several that were tuberculous. The owner withdrew their milk from sale, but, considering it would be a pity to waste so much of what he thought, at any rate, good feed for pigs, it was given fresh from the cow to the pigs. The result was that almost without exception the pigs became affected, and had to be slaughtered.
Some light, it is thought, has been thrown on the question by the fact that members of the Jewish religion, in communities where the meat eaten by them is subject to rigorous examination, and rejected unless the carcase is thoroughly sound, are much less subject to tuberculosis than other people in the same districts. In Melbourne and Sydney, according to Dr. McLaurin, there was during three years only one death from tuberculosis of the lungs among the Jews of these cities, while, if they had been affected in the same proportion as the rest of the population, thirteen or fourteen would have succumbed.
In many towns in Britain a considerable portion of the milk supply is provided by stall-fed cows, which are especially liable to tuberculosis on account of their unnatural confinement in the stalls, the generally unhealthy nature of their surroundings, and the exhaustion resulting from long-continued lactation. When diseased, these cows, being no longer fit for dairy purposes, are sent to the slaughterhouses, and their flesh utilized for food. So, too, cattle from other sources similarly affected. In the last stages of tuberculosis these cattle are known as “wasters,” from the most prominent symptom of their disease, or as “mincers,” from their ultimate destination, they being favourite purchases of the sausage-makers, whose agents in different parts of the country are able to pick up such animals at comparatively cheap prices.
If, however, danger exists from the consumption of meat from such animals the danger from using milk of tuberculous cows is much greater. Meat is cooked, and the germs thus often perish; but milk, as a rule, is used uncooked, and still more so its products, butter and cheese. It is possible by the inspection of a carcase to tell if the meat is unfit for food, but milk infected by the Bacillus tuberculosis requires a minute microscopic examination, which, as a practical dairy test, is
impossible. Further, in the cow the udder is especially liable to be affected by tubercle. In the human species the breast is rarely affected; but in the cow, very often while still “prime fat,” and before any symptoms point to the general system being affected, the udder is so diseased that the milk drawn from it is a dilution of tubercular poison. In a large dairy one tuberculous cow may be the means of carrying the disease to hundreds of families, all ignorant of the danger they are incurring.
To sum up our knowledge of the influence of the milk-supply in causing tuberculosis in man, we may say that it is proved that tuberculosis in man and in cattle are the same disease—due to the Bacillus tuberculosis; that the milk from a tuberculous cow, especially if the udder is affected, is liable to contain the germ of tuberculosis; that the use of food containing this germ has been proved a means of infection, and that therefore the use of milk from tuberculous cows is attended by serious danger. There is good reason for believing that the use of such milk is responsible for some of the tuberculosis in man, especially of its manifestations in children.
I have endeavoured to bring under your notice the principal diseases by which man may become affected through his milk-supply. A knowledge of the dangers incurred by this means is of value only so far as it is applied to lessen or prevent the risk of disease. I hope you will bear with me a few minutes while I attempt to point out the ways in which we may take advantage of our knowledge. In the first place, in all duties connected with the milk-business—its production, its distribution, and its consumption—cleanliness is a first essential, and in securing this the consumer as well as the producer must bear his part. In his own house he should insist on the milk being kept in perfectly clean vessels, and free from dust. He will gain much also from seeing that it is boiled shortly before use, unless he is positively certain that it is in every way pure. If he is cognizant of a want of cleanliness in the dairy from which his milk is derived he must, of course, take the responsibility of any evil results should he continue a customer of that dairy. The consumer is able to effect much good by insisting that his milk shall come to him from such a source and under such conditions that its purity is guaranteed. Unfortunately, the majority of milk-consumers either do not care from whence their milk comes so long as they get it, or else have no opportunity of inquiring and satisfying themselves that all due precautions are taken to insure that a good article is being delivered to them.
The chief responsibility in insuring a pure milk-supply rests with the dairyman, and, although there is no doubt that the necessity of avoiding the suspicion of supplying contaminated
milk exercises a salutary effect, yet I think we may safely say that it is a very small minority of milk-vendors who would knowingly distribute milk capable of causing disease. Most of those I have become acquainted with have shown themselves anxious to provide against dangers of this kind. Still, there are black sheep in every flock, and cases have come to light where milk has been deliberately adulterated with sewage from an open drain. Where the dairyman is at fault the deficiency probably arises chiefly from ignorance or carelessness, and until it is usual for dairymen to be proficient in sanitary science such causes must continue to operate. Hence the necessity that dairies and milk-shops should be under the supervision of some public authority, and that the law should demand that precautions be taken to insure a pure milk-supply. It is necessary to provide—
1. That cows whose milk is used for consumption by man should be free from disease:
2. That the sanitary arrangements of dairies and milk-shops and their surroundings should be complete:
3. That the water used for the cows should be good, and especially also that water intended for washing the teats before milking, and for cleansing the milk-cans and other dairy-utensils, should be such as man might drink with impunity:
4. That there should be proper appliances for efficiently cleansing all utensils in which the milk is placed:
5. That during its distribution the milk is kept from dust:
6. That all employed in dairies, or otherwise in the distribution of milk, should themselves be free from infectious disease, and should not come in contact with those thus affected.
In Britain, such provisions as these are in force, and to facilitate their being carried out it is provided also that each local authority should keep a register of all carrying on the business of cow-keepers, dairymen, or purveyors of milk. In some districts the Dairy, Cow-sheds, and Milk-shops Order seems to work fairly well, but it is now felt that further legislation is necessary, as almost universally there is great laxity in enforcing its provisions, owing to the want of efficient inspection. Dairies and milk-shops, as well as the cows themselves, ought to be subject to frequent systematic inspection by competent officials. There is also no provision against the importation of impure milk into any locality, although all dairies and shops within its boundaries may be rigidly controlled. For example, London dairies may be perfect, and yet milk of doubtful quality may be imported perhaps from the North of England without restraint. At present, in Britain, tuberculosis is not one of the diseases included among those which disable a cow from being used for dairy purposes.
The question as to whether it ought not to be included is now being discussed, and there is no question but that sooner or later the necessity will be recognized of preventing the sale of milk from tuberculous animals. The difficulties which at present lie in the way of such legislation are partly common to all attempts to legislate for the good of the community by controlling any special branch of trade. It is difficult to prevent injury to individual rights, and one serious part of the question is, whether compensation ought not to be allowed to the owners of cows which would thus be prevented from being a means of profit.
What the condition of the law in New Zealand may be with regard to the milk-supply it is difficult for one little acquainted with the statute-book to determine. Legal provisions on the subject are contained in clauses scattered through various Acts.
Adulteration of milk is provided against along with that of other foods. The Public Health Act contains a clause empowering the Governor in Council to provide for the registration of purveyors of milk, &c., for the appointment of inspectors, for the securing of efficient sanitation of dairies and milk-shops, and for the prevention of the sale of milk in cases where it would endanger the public health. Local Boards also may be authorized to make regulations for effecting these purposes. Regulations were gazetted to this effect in 1882. No practical result has, however, so far as I can learn, been the outcome of this part of the Public Health Act. There does not appear to be any registration of dairies; and only on special occasions, and then also only in limited districts, has any systematic inspection of dairies and dairy-cattle been made.
During the last session of Parliament some advance has been made by including tuberculosis among the diseases which when detected by the Inspector of Cattle necessitate the destruction of the animals affected. Tuberculosis, according to the report of the Live-stock Committee, is prevalent to a considerable extent in New Zealand, but accurate information as to the degree of its prevalence is still wanting. It is pleasing to find that the Live-stock Committee recognizes how serious a matter it is that tuberculosis should be prevalent in any country, and that the advice of the Committee has been acted on to circulate among stock-owners and others the admirable report on the subject drawn up in Britain by the Departmental Committee of the Privy Council.
In New Zealand we often congratulate ourselves that we are keeping up with the progress of the rest of the world. In sanitary matters generally we do not perhaps show quite as much activity as we ought, and in the matter of
regulating the sanitary surroundings of the milk-trade it is evident that we are sadly deficient. Wholesome official control of the milk-supply ought to be a powerful factor in maintaining the exceptional healthiness of the population, which is one of the great privileges of the colony, and our gain would be not only in the direction of physical welfare. We are hoping and attempting to develope an export trade in dairy-produce. Throughout the world attention has been directed to the dangers to health lurking in food derived from milk and its products; and other countries—Denmark, for instance—have seen the necessity of providing legislation which will help to guarantee the harmlessness of the dairy-produce they export. If New Zealand is behind the times in doing likewise she must struggle the longer in opening a market for her surplus dairy-produce.
I have offered nothing original in what I have brought forward. I have attempted only to give an idea of the views at present held on the subject of milk as a vehicle of disease, and I trust that the importance of the subject may veil any defects of the method in which I have treated it.