Batrachia. Formerly many zootomists regarded as supra-renal capsules those pecu liar yellow finger-shaped masses of fat, which, in these animals, lie superficially to the kid neys, and possess a connection with the sexual organs, in the periodical increase of which they take a share. Only recently have the true supra-renal capsules been recognised ; and to these the fatty bodies just mentioned have not the remotest resemblance. To Rathke*, Retzius t, Gruby $, and others, we owe the discovery and description of these organs ; the signification of which receives an additional and complete confirmation from minute anatomy, as will be hereafter shown. Here the supra-renal capsules no longer form an organ anatomically defined, but are imme diately deposited on the abdominal surface of the substance of the kidneys.
Among the tailless Batrachia, they appear in this situation as a golden-yellow streak, which does not extend the whole length of the kidney, but ceases at a distance of one line from its upper, and of two lines from its lower, end. These supra-renal organs also allow a lobular composition to be very dis tinctly discerned ; and they do not extend along the kidney in a straight line, but usually digress into the arched form. They surround the trunks of the efferent renal veins at their exit from the substance of the kidney ; so that they seem to be, as it were, perforated by this vessel. By a more careful investiga tion one may satisfy one's self that the glands are really imbedded in the coats of these vessels. In the tailed Batrachia, on the other hand, we no longer find the supra-renal capsules in the shape of this connected streak, but broken tip on all sides into from twenty to thirty separate and irregular lobules. These are seated, partly in the substance of the kidney at its inner border, partly between the kidney and the inferior cava ; while they are also partly deposited on the coats of the latter vessel, and the gland-lobules have the same relation to the efferent renal veins as in the tailless Batrachians.
Finally, amongst all the orders of Reptilia, the supra-renal capsules are least recognised in the Chelonia. The statements formerly made by Bojanus §, that the supra-renal cap sulcs were two long bodies, situated at the inner margin of the kidneys, and a similar statement of Nagel*, have been lately cor rected by Eckert According to the last in quirer, the supra-renal capsules of the Tea tudo greeca altogether correspond, both as regards form and situation, with the similar organs of the Frog ; since they lie on the abdominal surface of the kidney, imbedded in its mass, and extend almost the whole length of this organ.
In Fishes the supra-renal capsules again appear ; but, as regards their situation, form, and number, they are much more diverse than in the other Vertcbrata. The supra-renal
organs of the cartilaginous fishes were dis covered, a long time ago, by Retzius.$ For a knowledge of them in the osseous fishes, we are especially indebted to Stannius and Ecker.
In the osseous fishes they appear as small, whitish corpuscles, of the size of from a pin's head to a pea. Their form is, in general, roundish or oval ; their surface is sometimes smooth, sometimes rugged, and broken up into lobules, as is the case in the Pike. Ac cording to the observations of Stannius, they have not unfrequently a kidney-shaped form in the Haddock ; and, according to Ecker, they are sometimes triangular in the Salmon.
The number and situation of the supra renal capsules varies greatly in this group of fishes. The presence of two supra-renal capsules ought to be regarded as the rule. They usually lie symmetrically in both halves of the body, as in the higher animals ; they may also occur a-symmetrically, or only in one half of the body, as in the genus Pleuro nectes ; or they may be behind each other, as in the genus Scomber.
But frequently, the supra-renal capsules are present in great number ; in which case their position becomes altogether irregular. Thus one meets with three, four, six, or even more supra-renal organs ; and Eater has observed as many as six in the Salmon. In the Pike, in which only two to three supra-renal capsules are present in the adult animal, the inquirer just mentioned found that, in a young animal of one foot in length, the whole kidney vt as beset with a great number of very small saprn renal organs. I have myself remarked the same condition, and occurring exactly in the manner described, in two Pikes of the same size : but, on the other hand, in another in stance it was absent.
As to the situation of the supra-renal organs in the bony fishes, this also is subject to very great differences. Sometimes these glands lie more on the abdominal, sometimes nn the spinal, surface of the kidneys. The former seems more frequently to happen ; and in this case they generally project at the hinder end of the kidney, from the anterior margin of the hmmal canal of the inferior vertebral arch : this occurs in the genera Cyprinus, Tinca, Pleuronectes, Anarrhichas, Scomber. Or they occupy more the middle of the kidney, as in the Salmo Salar. On the other hand, they are found on its abdominal surface in the Eel and Pike. They lie in this situation very anteriorly, occupying, in the Eel, the place where the two crura of the renal mass unite. In the Pike they are yet more advanced forwards, so that they come to lie in the middle point of the length of the body.