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Volume 31, 1898
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Art. XVIII.—Notes on certain of the Viscera of Notornis.

[Read before the Otago Institute, 13th September, 1898.]

Plates XII.–XIII.

On the arrival of the fourth specimen of Notornis the viscera were removed by the taxidermist attached to the University Museum (Mr. E. Jennings), and I proceeded to make an examination of such organs as were likely to be of general interest to ornithologists. I regret that I was unable to dissect the bird in a thorough-going and careful manner, but the necessity for preserving the skeleton, and for doing as little injury as possible to it and to the skin, prevented me making as exhaustive a study as I should have wished.

I may mention that this is the first opportunity that has presented itself to any naturalist of examining the internal anatomy of this bird, and I have deemed it of sufficient importance to communicate my observations, accompanied by drawings, to the Zoological Society, in the Proceedings of which they will in due time be published. This will render unnecessary the reproduction of all my drawings in the present communication.

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The entire viscera have been carefully preserved in alcohol for future reference or for further study.* An examination of the genital organs revealed the fact that the specimen was a young female; the ovary was small, and none of the eggs exceeded 1/8in. in diameter.

I made a special study of the following viscera: (a) The alimentary tract; (b) the larynx; (c) the syrinx.

(a.) The Alimentary Canal.

The œesophagus and glandular stomach present no features of special interest; but the, great size of the gizzard seems noteworthy: it measures 3 ¼in. by 2 ¼in., the larger axis, of course, being obliquely transverse. It is of a character usual in graminivorous birds, having very thick muscular walls and

[Footnote] * The contents of the gizzard were submitted to Mr. G. M. Thomson, who kindly volunteered to examine the fragments of “grass” which formed the bulk of its food. Mr. Thomson writes to me as follows: “It is almost certain that the bird has chiefly fed on species of Carex and Uncinia (cutting-grasses), and what strengthens this view is that these plants are particularly common at the edge of the bush…. At the same time, there probably are some pieces of true grass among the debris, but I looked at over a score of pieces and they all belonged to the Cyperaceous type.”

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a thick hard lining within. The latter, as is frequently the case, is continued beyond the thick muscular wall into what appears externally to be the commencement of the intestine.

The intestine measures 48 in. from the pylorus to the point of entrance into the cloaca, from which it had been cut by the taxidermist. The loop of the duodenum measures 5 ½in., and has a diameter of ¾ in., the remainder of the gut being slightly narrower. The intestine beyond the duodenal loop is thrown into two large and two smaller U-shaped coils, as in the Rallidœ generally. Unfortunately, I was unable to map these out with absolute accuracy in the manner in which Mr. Chalmers Mitchall has done for a series of birds,* as the mesentery had been injured before I examined the viscera, but I have represented them in what appears to be their natural position; but it is needless to describe their arrangement in the present paper. I would refer those, interested in the matter to my forthcoming paper in the “Proceedings of the Zoological Society.”

There is a vestige of the vitelline duct, about ½in. in length, at a distance of 24 in. from the gizzard—in other words, at a point half-way along the intestine, at the apex of the second post-duodenal loop. The paired cæca are of considerable length; measuring 9 in. They arise at a point 6 in. from the hinder end of the gut. Each cæcum has the normal shape and arrangement, commencing as a narrow tube and dilating gradually to form a thin-walled terminal sac.

The liver has, as usual, its right lobe larger than the left. The gall-bladder is entirely free from the liver.

There are two bile-ducts, as is generally the case in birds. One of these, since it arises directly from the left lobe of the liver, is known as the “ductus hepato-entericus,” or “hepatic duct,” to. distinguish it from the “cystic duct,” or “ductus cystico-enterieus,” which is connected, with the gall-bladder. This latter duct (Pl. XIII. fig. c.d.) runs down the mesentery alongside the distal limb of the duodenum, into which it opens on its dorsal surface close to the apex of the loop. The other, or direct hepatic duct, passes along the middle of the mesentery, to open ventrally into the gut close to the former.

The pancreas presents three lobes or regions. The basal lobe is brownish in colour and less compact than the other two, which are yellow (Pl. XIII. fig. p.b.). It lies adherent to the duodenal mesentery throughout; on its ventral surface it carries the ventral lobe, which extends beyond the basal lobe forwards to form a finger-shaped process projecting freely from the mesentery, and backwards forms a rounded, broader

[Footnote] * Proc. Zool. Soc, 1896, p. 136.

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lobule, overlying the ventral surface of the apex of the duodenal loop. The dorsal lobe of the pancreas (p.d.) is connected with the basal lobe at its posterior end, and runs forward on the dorsal face of the mesentery, close to the distal limb of the duodenal loop. It is only about half the length of the ventral lobe, and its posterior end overlaps the intestine, as that does.

There are in Notomis, as in some other birds, two pancreatic ducts—one connected with the dorsal lobe and one with the ventral lobe. The ventral pancreatic duct (p.v.d.) arises from the posterior rounded flap or lobule of the ventral lobe of the pancreas, runs across the mesentery, passing ventrad to the hepatic duct, and enters the distal limb of the duodenum just beyond it. The dorsal pancreatic duct (p.d.d.) springs from the dorsal lobe, and opens into the duodenum close to the cystic duct.

It seemed worth while to examine the tongue with some care and detail, as there can be no doubt that this organ in birds is of great interest and importance. I have given a drawing of it in my paper in the “Proceedings of the Zoological Society,” and will not describe it here, as a mere account of it would be tedious.

(b.) The Larynx.

The larynx is imperfectly ossified, and suggests at once the immaturity of the bird. Detailed figures are given in my other paper.

The glottis is provided with a rudimentary epiglottis in the form of a small rounded cartilaginous knob, slightly overhanging its anterior angle.

The thyroid (or, as recent authors term it, the “cricoid”—refusing to acknowledge its homology with the thyroid of mammals) is a nearly flat, but slightly spoon-shaped, bone, about twice as long as broad, feebly convex ventrally, slightly pointed anteriorly, and truncate behind. The posterior half of its lateral margin is slightly upcurved, and forms a ridge, to which is articulated a bone of nearly rectangular outline, but sharply curved inwards dorsally, so that it nearly meets its fellow of the opposite side, from which, however, it is separated by a median hexagonal bone forming the posterior (dorsal) wall of the laryngeal cavity. It is interesting to note that the rectangular-curve bone is independent of the spoon-shaped bone, for, according to Tiedemann, Dumeril, and other authorities, this posterior piece of the thyroid becomes continuous with the main part of that bone in old birds. This fact again points to the immaturity of our specimen of Notornis.

The median hexagonal bone is the “cricoid” of older

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ornithologists (or “procricoid” of Fürbringer and other recent writers). It is grooved on its dorsal or posterior face, and laterally receives each of the posterior pieces of the thyroid in a rounded notch. On its upper or anterior face it further articulates with the pair of arytenoids.

Rach arytenoid is nearly Y-shaped, the stalk of the Y being directed forwards and the fork backwards.* This Y-shaped bone is, however, curved, so that the outer limb is concentric with the margin of the thyroid, and the inner limb (which is incompletely ossified) bounds the glottis. The posterior end of the outer limb is sharply curved inwards to articulate with the cricoid.

I have described the larynx in some detail, as there appears to be no easily available account of this organ in birds.

The tracheal rings, which are incompletely ossified, overlap one another alternately right and left. Each ring is narrow in the median, dorsal, and ventral lines, but widens out laterally. Any given ring overlaps its successor on one side—e.g., right—but is overlapped by it on the other side—e.g., the left, or vice versâ. I noted a structure that appears to be of some interest in connection with, these tracheal rings—namely, that on the dorsal median line a small nodule of cartilage lies above the narrowed part of each ring; or, rather, the nodules alternate with the rings at this point, but lie more superficially.

(c.) The Syrinx.

The syrinx, or lower larynx, consists of seven closely apposed rings, of which the fourth carries the pessulus, and. appears therefore to be the last tracheal ring (according to Gadow, in Bronn's “Thierreichs: Aves”); consequently, the syrinx is composed of four tracheal and three pairs of bronchial rings.

The membrana-tympanica externa is supported by the last syrinx ring and the three next bronchials.

All the syringeal rings are separate, again indicating, presumably, the immature condition of the bird.

The first syringeal ring (a) differs but little from the preceding tracheal rings; it is, however, stouter. The next ring (b) differs from the preceding ones in being incomplete dorsally, where each end abuts upon a dorsal cartilaginous

[Footnote] * Whether or not the anterior end articulates with the thyroid I was unable to determine, as I did not wish to injure or displace the structures more than I could help. I have had to content myself with an examination of one side of the structure only, so that if the bird passes into the possession of a competent ornithologist he may be able to look into such details as are of real importance. As I have no special knowledge of bird-anatomy from the point of view of the systematist, I have purposely done as little damage to the structures as possible.

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plate, in which ossification is just commencing. The third ring (c) is somewhat larger, and its dorsal extremity on either side curves round the bronchus. The fourth ring (d) is stouter than the rest; ventrally. it presents a rounded knob, which is produced downwards between the two bronchi: thence it is continued dorsally, as the pessulus, in the angle where the trachea divides to form the two bronchi. This ring (d) is, like b, c, incomplete dorsally, the right and left extremities curving round the upper part of each bronchus, to cease at the membrana-tympanica interna.

The pessulus is a straight long rod, continuous at its ventral end with the ventral knob of the ring (d), but terminates dorsally against a couple of small ossicles (r), which are not connected with any ring, though possibly they do become co-ossified with one in the adult bird.

The remaining rings of the syrinx (e, f, g) call for little remark; they are incomplete internally, and embrace only the outer surface of the bronchus, the inner surface of which is formed by the membrana-tympanica interna. These three bronchial half-rings are closely apposed externally, and the lower margin of g is concave backwards. Between it and the next bronchial ring (i), and between (i.) and (ii.) and between (ii.) and (iii.), is stretched a thin membrane, the membranatympanica externa. Then follow normal bronchial rings. From the restriction of this membrane to the side of the bronchus this kind of syrinx is termed a “bronchial syrinx.”

This apparatus of Notornis does not closely agree with any that are figured in Bronn's “Thierreichs” by Gadow, nor with other figures with which I have compared it; hence I have described it in some detail. The syrinx which is least unlike that of Notornis is that figured by Beddard for Ægotheles novœ-hollandiœ, so far as the arrangement of the membranatympanica externa is concerned.

There is one point in which Notornis appears to be unique, though I am willing to admit that this may be due merely to my ignorance of avian anatomy. According to Gadow (in Bronn's “Thierreichs”) the ring which carries the pessulus is to be regarded as the last tracheal. Now, as I have stated, the ventral end of this bone springs from the fourth ring, which is therefore tracheal; yet the dorsal ends of this same ring undoubtedly belong to the bronchi, round which they curve, for here indeed they are separated from the trachea by the dorsal ends of the third ring. Consequently, a ring is both tracheal and bronchial. This is a matter of interpretation; the facts are certain.

Connected with the larynx various muscles have been-described. Of these, one, the bronchio-desmus, is stated to be constant. However, I have failed to recognise it, unless

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it be represented by a structure partially membranous partially muscular which passes from the lower region of the membrana-tympanica interna, on each side, to the wall of the œsophagus.

The only other muscle which exists in relation to the syrinx in Notornis is the tracheo-bronchialis, which is attached to the side of the ring (d).

Explanation of Plates XII., XIII.
Plate XII.

General View of the Viscera.

  • b.w. Body-wall.

  • c. End of one of the paired intestinal cæca.

  • d. Portion of duodenum.

  • G. Gizzard.

  • g.v. Gastrohepatio vein.

  • I. Intestine.

  • L.L. Left lobe of liver.

  • P. Pancreas.

  • R.L. Right lobe of liver.

  • st. Stomach.

Plate XIII.

Fig. 1.—View of the Duodenal Loop, with, Liver turned forwards.

  • c.d. Cystic duct.

  • G. Gizzard.

  • G1. Short continuation of gizzard.

  • g.b. Gall-bladder.

  • h.d. Hepatic duct.

  • L.L. Left liver lobe.

  • p.b. Basal portion of pancreas.

  • p.d. Dorsal lobe of pancreas.

  • po.v. Portal vein.

  • p.v. Ventral lobe of pancreas.

  • p.v1. Free projection of same.

  • p.v.d. Ventral pancreatic duct.

  • py. Pylorus.

  • s.l. Suspensory ligament.

Fig. 2.—Posterior Portion of Duodenal Loop, seen from the Dorsal Surface.

  • c.d. Cystic duct.

  • p.b. Basal portion of pancreas.

  • p.d. Dorsal lobe of pancreas.

  • p.d.d. Dorsal pancreatic duct.