The supra-renal capsules of the Mamnialia essentially correspond with this description.: They are always situated on the upper part of the kidneys ; sometimes towards the inner part, sometimes on the upper part of their border, as in man. Sometimes they are not so closely attached to the urinary organs as in man, but are somewhat more removed from them. Thus, for instance, are arranged the supra-renal capsules of the Elephant and Seal. But, in opposition to this constancy of situation of these organs, we find very considerable differences in respect of their size and form.
The supra-renal capsules of Monkeys closely approach the shape seen in the human sub ject ; but, not unfrequently, their size seems somewhat more considerable. Among the Carnivorathey are, in the Dog, of an elongated cylindrical form, sometimes thicker at the margin than in the middle, and of a dense solid texture. So also in the Cat, in whom they are roundish, and somewhat flat tened. Amongst insectivore they have in the Mole (Talpa europoa) the form of a three sided pyramid. In the Seal they appear very small, and envier found that their size was, to that of the kidneys, as 1-150. In this latter animal the whole surface of the supra-renal capsules is divided into a multitude of lobules, or acini. Amongst all the Mammalia, these blood-glands are largest in the Rodentia, their ratio to the kidneys being as 1 to 4 and 5 : this is the case, to wit, in Ccelogenys Paca, and in the Guinea-pig (Cavia cobaia). They are roundish, and somewhat flattened, in the Rabbit and the Dipus. The supra-renal cap sules of the Mouse, the Rat, and the Myoxus Glis, have a shorter form ; while, on the other hand, in Hystrix they become more cylindrical.
Amongst the Paehydermata they have, in the Elephant, the form of an elongated cone, and their base is divided into two lobes, and turned backwards. In the Pig, their form is about midway between the cylindrical and the pris matic. Besides this, the supra-renal capsules of this animal possess a considerable size. In the Horse they are flattened and triangular, approaching the human form. Among the Ruminantia they are, in the Rein-deer, of an oval form, which approximates to the sphe rical. They are elongated in the Sheep. In the Ox, their shape in some degree resembles that of the kidney. Here they are almost crescentic, not unlike a horse-shoe, and their upper extremity is three-sided. Finally, the sup-a-renal capsules of Cetaceans are, like those of the Seal, exceedingly small, and broken up into a number of small lobes.
We find a similar correspondence in the class of Birds. Their supra-renal capsules are generally small in proportion to the size of the body ; sometimes spherical, sometimes oval ; and, in general, divided into lobules. They lie at the inner extremity of the anterior part of the kidney, often close to the inferior vena cave ; and they are covered by the tes ticles, or ovaries.
In the fleptille these organs are much less known, since only isolated (and not unfre quently contradictory) observations have been made respecting them. Hitherto they have not been found among the Derotremate, Pe rennibranchiate, and Ctecilian orders of this class.
The supra-renal capsules of the Saurians have been very eagerly examined, and most exactly in the genus Lacerta. In these ani mals Nagel found them along the upper ex tremity of the vas deferens, in the form of two long, small, lobulated bodies, Nagel's obser vations have been recently confirmed, and added to, by Ecker. The supra-renal cap sules, possessing the form stated by Nagel, have a length of 11 lines, with a breadth of They lie closely on the vena renalis re vehens, or on the vena cava ascendens, which is constituted by the two efferent renal veins. Since the right supra-renal capsule is usually of somewhat larger size, it is wont to lie on the vena cava itself; while the left organ is placed upon the vena renalis revehens. In the male lizard the supra-renal capsules are placed between the vein and the vas deferent ; in the female they are situated between that vessel and the ovary. Numerous blood-ves sels convey the blood from it into the corre sponding wins. The blind worm (Anguis fragilis) also possesses long, small, sura-renal capsules ; and so, probably, do the Crocodilus Lucius and Ameiva tegui.rin. Nevertheless, both the latter animals are at present insuffi ciently examined.
The supra-renal capsules of the Ophidia ex hibit a similar condition, the more exact knowledge of which we especially owe to Retzius. They form two long and small bodies, and in the Python binistatus they at tain a length of 8 lines. The supra-renal capsules of serpents are likewise distinctly lobulated, and very vascular. In other re spects, too, the arrangement of the vascular system exhibits much that is interesting ; but to this we shall hereafter return. They always lie closely on the venm renales abdu centes ; and, according to the course taken by the vessels just named, they are sometimes nearer, sometimes farther from, the testicles and ovary.