SUPRA-RENAL CAPSULES. (Die Kebenniere, Germ. Capsular suprarenal(s seu atrabilarice, Lat. Capsules suprarenales, atra hilaires, Fr.)— In the bodies of Vertebrata we find a series of organs, which possess a great outward resemblance to the glands, but distinguish themselves from these by the constant absence of a duct. To this class belong the spleen, the thymus, the thyroid, and the supra-renal capsules. On account of their great richness in blood-vessels, these organs have been named " blood-glands," or " glands of blood-vessels," or "vascular gang lia." At present we are tolerably acquainted with the range of their distribution, and the differences of their form in the animal king dom ; we have, also, some knowledge of their minute structure ; but, on the other hand, their physiological import remains just as ob scure to the inquirers of the present century as it was to the physicians of ages long gone by.
The supra-renal capsules, glanduhe supw renales sea renes succenturiati, seu capsular atrabilarice, form, in the higher Vertebrata, a double organ, which is constantly placed in the neighbourhood of the kidneys; and from this situation they have received their name. So, also, in the lower Vertebrata they of'en occupy the same situation ; but, not Infre quently, they are broken up into a number of small glandular bodies. In the Invertebrata they are altogether absent.
We shall successively consider, I. The larger series constituted by the differences of form of supra-renal capsules in the animal kingdom. 2. Their structure. 3. Their de velopment. 4. Their physiological relations.
I. As already mentioned, supra-renal cap sules occur only in the Vertebrata. But we cannot attribute them to all of these without exception. In the lowest Amphihia and Fishes, these organs have not yet been indubitably recognised. Among the Mammalia, the supra renal capsules exhibit everywhere essentially the same structure, in spite of many differ ences of form, size, and situation.
In Man they possess a half-moon shaped, or triangular and flattened form, with an an tero-posterior slightly arched surface, and a sharp convex margin. At their bases they
are deeply excavated, so that by this part they rest on the upper end of the kidney like a cap. The anterior part of the basis of the supra-renal capsule extends for a considerable distance further forwards on the kidney than the hinder part. The whole organ is included in a covering which consists of closely woven areolar tissue ; and inferiorly, it is attached by a looser areolar tissue to the kidney. At the base of the organ is also found a well marked fissure, from out of which passes the supra-renal vein, according to Krause's state ment.* The anterior and posterior surfaces of the suprarenal capsules exhibit an irregu larly wrinkled appearance, caused by the nu merous furrows of the areolar tissue. The size of the supra-renal capsules amounts in the adult to 1-11 inches (German) in height, and somewhat less in breadth. The greatest antero-posterior thickness occurs in its lowest part, and amounts from 2I-4 lines. In their middle the supra-renal capsules are consider ably thinner, amounting only to 1 —24. lines. Their absolute weight is estimated by Meckel to be one drachm : according to Krause* it is from 80-120 grains; according to Huschket from 80-180 grains. The anatomist last named found that its specific weight in the newly-born infant was 1.0333 ; but Krause states the supra-renal capsules of the adult to be of the somewhat lower specific gravity of 1.0163.
The two supra-renal capsules of the same individual are generally of different size. Usually the right is of somewhat lesser height, but greater breadth, than the left, which has the contrary diameter the larger.
The so-called accessory supra-renal capsules are often found in man. They are small round corpuscles, which, in various numbers, are attached loosely to the inner border of the supra-renal gland, or are sometimes im bedded in an excavation on its surface.