good country and then returning them to the unhealthy country settlers may keep their stock in good condition. Park here gives the advice that every medical and veterinary practitioner would probably have given in an isolated case of anaemia to try iron medicine as the natural remedy for such cases. “If some of the settlers would take sufficient interest in their stock and administer carbonate of iron, we might see what could be done to improve the cattle on the pastures without removal, but until they do so and attend to details, I fear we must rely on what has been successful in practice, viz., change of pasture.” He further (p. 92) discusses the same disease in sheep occurring at Tauranga. In this case also, he was unable to find any organic disease, and the experience is recorded that as in the case of cattle (at Arahiwi) the sheep do well for a time and fatten, but after five or six months pine away and if not removed soon die. “On the suggestion of Mr. Clifton, one pet lamb was treated with Parrish's Chemical Food (Syrup of Phosphates of Iron) and was said to improve a little but eventually pined away and died. Probably the green carbonate of iron as prepared by Burrows and Welcome may be found a suitable remedy, for it is said to be successful in the human subject in cases of anaemia, and very reliable.”

Park's suggestions are given in extenso as showing that although he was alive to the remedy on general grounds for treating anaemia, the cause was yet to be determined. Anaemia may be caused by slow poison as well as by starvation, and until that “something wanting in the soil” as he puts it, or as we now should say, something wanting in the pasture, is ascertained, no logical treatment of the animal or pasture can be prescribed.

It was not until the iron sulphate-top-dressed pasture proved on sheep so efficaceous in the Lichfield experiments, 1911/1912/13. (9) that the trial of iron medicines was indicated as a logically correct remedy for bush sick stock. The recovery of a ruminant under administration of iron remedies necessitates a long and tedious, treatment—a matter of weeks rather than days elapsing before any improvement can be noticed. It is doubtful whether any advice to give iron medicine would have been persisted in had not the treatment been dictated by evidence provided from the chemical analysis of many samples of soils, pasture plants, and animal specimens, culminating in the successful Lichfield experiment. Again, when laying down that experiment, sulphate of iron was possibly the last thing that one would have thought of for a top-dressing unmixed with other manures unless iron deficiency were suspected. Hence it will be seen that any advice involving long and tedious treatment, is likely unless supported by strong reasons to be disregarded as, in point of fact, Park's advice in 1898 to try iron remedies was disregarded.

After mentioning the existence of the problem in the 1897 report, p. 68, where he used the word “pining,” ^* Gilruth, (3) 1899 recorded his examination of a few cases of “Tauranga or Bush

Sickness.” Two sheep and one cow “revealed absolutely nothing which could be determined as causative of the progressive anaemia characteristic of the complaint.” He speaks of the interest and perplexity of this disease and “promises experiments the following year.” The experiments (4) are given in the 1900 report and are exceedingly interesting. The results have never been satisfactorily explained. Briefly they consisted in taking fifty sheep in November, from what were considered to be the worst of the mob belonging to the Thames Valley Estate and placing them on unhealthy^* land similar to country where they had been on since August. Thirteen of these sheep were taken to what is now Te Kauwhata in healthy country (a heavy clay loam soil) 109 miles from the unhealthy country, and placed on a bare ploughed paddock. Green food from affected land was cut and railed two or three times weekly to the 13 sheep on the bare paddock. These were in such a low condition when they arrived that some of them had to be carried from the trucks to the paddock. The fodder sent was coarse over-ripe grass, chiefly Yorkshire fog with a little fox-tail and red clover, and being sent only twice weekly was apt to heat before being used, yet the sheep improved in condition with the exception of the three very bad cases which had to be carried to the station. These lived a fortnight before dying. Unfortunately no post mortem was made. About a month after these were placed at Te Kauwhata, those in the “bush sick” area were inspected and a dozen found to have died, post mortem on one by Clayton showing anaemia with fatty liver but no other lesion. Gilruth visited the sheep in February, and found no trace of food growing on the paddock at Te Kauwhata, the animals being fed entirely on food now arriving three times a week, but not in quantity calculated sufficient to fatten any animal. The sheep were in poor condition but with a general appearance of health, and, were feeding with avidity on the fodder from the unhealthy country, thus having food similar in all respects to those on the unhealthy country, the only difference being the water supply. Gilruth next visited the control animals left in the bush sick country. In a small paddock under the immediate control of Mr. Wrigley, Tarukenga, who periodically forwarded the fodder to Te Kauwhata, all were found to be affected. One sheep had died and the others were emaciated and weak. Post mortem examination gave the usual result indicative of bush sickness. On the other paddocks in the bush only twelve sheep could be mustered out of the forty-two placed there in November, and these were similar to Wrigley's poor and emaciated, and post mortem gave the usual bush sickness indications. This experiment satisfied Gilruth that the herbage grown on the so-called sick country is not in itself inimical to the health of stock. Gilruth concluded that the remedy was to be sought for in a change in the system of management rather than in drugs or treatment of the land, at

least so far as sheep are concerned. He could only endorse the treatment already adopted by settlers in the district, of periodical changing of the stock from “sick” to what is known to be “healthy” country every few months. He quotes a report by the present writer showing that there was no poison in the water the stock drank, or in the pasture they ate, or the soil on which the pasture grew. These are the only occasions that Gilruth mentions the matter in his published report. Although he did not leave the Department's service until 1909, “bush sickness” is not again mentioned. On two occasions when he mentions it he uses the word “perplexing” and he wisely expresses no opinion as to the cause. It must not, however, be thought that this silence meant that nothing had been done. As a matter of fact much work was done but never published. Transfusions of blood tests and many post mortems were carried out by Gilruth, Clayton and Lyons, veterinarians assisted by Robert Alexander, subsequently Stock Inspector in charge of the Waikato. The names of these men are sufficient guarantee that the matter was thoroughly investigated from a veterinary point of view.

Official unpublished records show that in 1903 Gilruth reported:

“As a result of these experiments, I arrived at the following conclusions:—

In 1905 (5) the writer reports having recently visited the bush sick area and collected samples of soils and blood of the affected animals. The bloods were taken by Clayton and Lyons from animals diagnosed as being in advanced stages of bush sickness. Previous to this, many analyses (6) had been made of the soils, pasture ash, and waters from the sick country, and are to be found in the Chemistry Division Reports, but they were made chiefly with the view of detecting any poisons which might be contained in the soil or the herbage, and so be consumed by the animal and lodged in its tissues. The idea of copper, the only element found to which suspicion could be attached, as being responsible was fully tested (6 “The Chemistry of Bush Sickness”) and finally the possibility of there being any mineral poison respon-

sible was abandoned after exhaustive tests; see Dominion Laboratory Report (7) (15).

In the case of a mineral poison, it is difficult to believe that if this were being ingested with natural food, i.e., pasture, that the addition, of a small amount of imported oats, bran, or linseed to the animals' diet would prevent the poison from ultimately exercising a poisonous effect on the animals. In the case of an organic poison, it seems improbable that the same compound could be produced in such differently related plants as the grasses on the one hand and the clovers on the other, and yet animals seem to develop bush sickness both on pasture which is largely clover or when it is largely grasses. There is also the difficulty of imagining any poison which could affect all ruminants and not other domestic herbivores, e.g.,. horses which remain continuously healthy on those types of soil growing the pasture which is most fatal to ruminants.

The field for enquiry was now narrowed down to the search for a deficient element in the food-supply. The analysis of the blood of animals in an advanced stage of “bush sickness” had shown that the elements phosphorus, potash and iron, characteristic of the blood corpuscles, were deficient (6). It was not to be thought that potash could be deficient in the food, as it was an abundant constituent of the pumice soils, and clovers (which absorb quantities of potash) are always present in the pasture of the affected country. For a considerable time, attention has been focussed on the possibility of phosphoric acid being the deficient element, a line of investigation which was sanctioned provisionally by a well-known professor of pharmacology whom the writer consulted personally in 1903, in England, and who gave it as his opinion after hearing the symptoms that the trouble was caused by an abnormality of the salts of the food. Accordingly in most of the experiments laid down on farms leased by the Department of Agriculture in the Rotorua county for finding a practical solution through application of top dressing to the pasture, phosphates were extensively used. This phosphate-deficiency hypothesis was supported by analysis of the soil and of cocksfoot grass, which was shown to contain a smaller amount of phosphate than is usual when grown on ordinary healthy country (14). Analysis of the sick animals' bones failed to show any deficiency of phosphate; moreover bone trouble has not been found to be a symptom connected with bush sickness, and one would expect a deficiency of phosphate sufficient to cause the death of a ruminant to show itself by malnutrition in the bones, which are the repository or storage organs for phosphates in the animal (20).

Experiments (8) with steers on pasture, which had as much top-dressing super-phosphate supplied as 7 cwt per acre, showed that although the animals benefited by the increased nutritive value of the pasture they could not be kept permanently healthy by that means. In two cases, bearing in mind the deficiency of iron found in the blood of the affected animals, the writer's suggestion was adopted and iron sulphate used as a manure to supply that element possibly deficient in the pasture.

Experiments (9) with sheep at Lichfield are recorded as follows:—“It will be noted that with sheep the best results were obtained from those depastured upon paddocks top-dressed with iron sulphate.” In this case the ewes kept in excellent condition throughout and reared their lambs successfully with one exception, and that lamb had reached good marketable condition and could have been profitably sold before any indication of bush sickness was manifested by it. Further on the other two experiments in series 4 where no iron dressing was used all the lambs died; and in the adjacent control paddock not only did all the lambs die but also all the three hoggets and two of the five ewes on it. In the case of the other iron sulphate experiments with sheep it was unfortunate that one of the two animals used, died through accident. The other, however, maintained excellent health and condition for a long period, ultimately dying of bush sickness in January, 1913, nearly two years after it had been placed on the paddock at Martin's, Mamaku (series 3). That these experiments with iron sulphate were subsequently discounted by experiments with sheep where the treatment did not prove efficaceous somewhat hindered the investigation, as in the eyes of the practical man the results appeared indefinite; but in the mind of the chemist two successful pasture experiments strengthened the suspicion that absolute deficiency of iron in the pasture was the cause of “bush sickness.”

A new Director of the Veterinary Division, Dr. Reakes, had been appointed to succeed Gilruth in 1909, and had personally directed the field experiments with animals on different leased areas of “bush sick” lands. The leased areas were finally abandoned in favour of a Departmental farm at Mamaku for the sole study of the problem. Then came the war with the shortage of men, and the depression afterwards with shortage of money. This may be said to have thrown the investigation back some ten years; for it is not till 1924 that the writer (10) was able with any confidence to begin a series of articles in the Journal of the Department of Agriculture, setting forth a reasonable theory.

In 1912 (20), the writer had stated “about eight years^* ago I made analysis of sick animals' blood and found it extremely deficient in iron. Subsequent tests (6) confirmed that analysis; this together with analysis of soils and grasses, hinted that a deficiency of assimilable iron in the food might be the cause of the sickness. This suggested the application of iron compounds to the soil as a possible remedy. When therefore asked to suggest a series of schemes for top-dressing the pastures of the affected country, iron sulphate was recommended by me for two farms situated widely apart. It is significant that of all the substances experimented with iron sulphate applied alone to pasture has been the most successful in enabling sheep (the animal most susceptible to the sickness) to be kept healthy over a period of 18 months. This is the more remarkable as of the substances tried, phos-

phates, lime, potash, nitrates, and iron sulphate, the last is the one which would possibly not have been thought of had the analysis not suggested it. The opinions generally expressed by authorities are not favourable to the use of iron sulphate as a manure. Although essential to plant-growth, iron is required in such minute quantities that all soils are thought to contain sufficient. When iron sulphate proves beneficial, the result is generally regarded as due to an indirect action and not to the supply of the plant food, iron.”

Another successful experiment in the use of an iron compound as a top-dressing was carried out at the Mamaku Farm. In this case the spent iron oxide from the gasworks was used, and the animals—sheep—were kept healthy for nearly two years on the paddock to which no other dressing had been applied.

During the interval in the research caused by the war, one thing had been proved. The administration of a suitable iron salt to a cattle beast in the proper proportion over a fairly long period would absolutely cure bush sickness, the food of the animal remaining unchanged. This discovery (11) was the direct result of the Lichfield experiment in indicating that iron was a remedy when applied to the pasture, and this in turn was the outcome of the analysis of the diseased animals' blood. The iron remedy first used with success was the syrup of phosphate of iron. Other iron salts were tried with a view to the adoption of one more easy to make and handle, notably the lactate, the tartrate and the double salt iron and ammonium citrate. No success was obtained at all with the lactate, but the tartrate gave good results, and finally the iron ammonium citrate was adopted and found perfectly reliable as a cure (12). This was a great step forward in the knowledge of the disease, and one which undoubtedly points to iron as being the deficient element in the food supply. Of the three radicles in this salt, iron, ammonium, and citric acid, iron is the only one likely to be deficient, since both ammonium and citric acid can be ruled out as a possible cure. The former has actually been tried as an ammonium chloride lick without effecting any improvement in a sick animal, and citric acid is present in all pasture.

It should here be pointed out that the anaemia is different from the isolated cases occurring in every medical practitioner's experience, where one individual in a group all getting the same food, becomes anaemic. In the case of “bush sickness” all the animals on the worst type of country will become in time anaemic, and if not removed or treated with concentrated food or medicines, all will assuredly die. With the iron treatment, if the animals, however badly affected, can be kept alive for a fortnight after the treatment commences, they will invariably recover.

Analyses of pasture plants collected in 1913 and 1914, from healthy and sick country clearly showed great differences in the iron content of the ash (13). In 1914, the writer again consulted an eminent British bio-chemist, who listened patiently to the description of the symptoms of “bush sickness” and finally said

It is therefore desirable in studying the mineral composition of pasture to consider the effect of one varying condition at a time, the other conditions being as far as possible kept constant.

Accordingly, in the following account an endeavour is made to arrive at the truth, the enquiry being limited to three species of plants growing upon three or four types of soil in the same county, on both manured and unmanured ground. The stage of growth has been limited to what is known as well-grazed good cow-pasture and the samples, taken as far as possible throughout the whole year, have been carefully selected by Mr. Grimmett or the writer. They were cleaned of any sandy matter by quickly washing in water, a proceeding which may have resulted in loss of potash and soda, but these were not in any case estimated, and the error in other constituents estimated from washing is probably negligible. After drying, the samples were sent to the Wellington Chemical Laboratory where they were carefully picked over, neglecting woody stalks and any material foreign to the species being analyzed. In this way it is hoped that the botanical purity is guaranteed, but that the freedom from earthy contamination can be assumed is more than can be hoped. In some cases earthy impurities seem to adhere so tenaciously to the leaves that they cannot be eliminated by washing. After air-drying, the samples were dried in the hot water oven to a brittle state, which enabled the portions to be broken in the hands to a state fine enough for ten to twenty gram portions to be weighed with every probability of obtaining a fair sample.

In analyzing samples of fodder plants it is desirable to establish the presumption that a sample is pure and free from such contamination of earthy particles as would appreciably affect the results of any analysis for mineral foods it is sought to estimate. This precaution is especially necessary in the case of elements such as iron or manganese which exist to a much greater proportion in the soil than they do in the tissues of the pasture plant living on that soil. It is probable that ruminants cannot assimilate such mineral foods when they are present as earthy contamination.^* Such minerals it is thought must first be absorbed and be present, in the tissues of the plant before the animal can absorb them. Iron, for instance, may exist in amount about one per cent. in a pumice soil and is extracted by the hydrochloric acid used in dissolving the plant ash. The amount of iron present in the tissues of dried grass is about 0.01 per cent. or one hundredth of what it is in the soil. It will easily be seen that a very small contamination of the grass with soil will make a very large error in the