THE URINARY APPARATUS. 579 



capsules receive a large quantity of blood, compared with their small volume. 

 The arteries are branches of the neighbouring vessels — the mesenteric and renal. 

 They form a very delicate plexus in the parenchyma. (They keep to the stroma 

 of the trabeculae ; consequently, their finest ramifications are found in the secou- 

 daiy septa of the cortical substance, where they form elongated plexuses, which are 

 rounder in the medullary portion. In the middle of the latter, the venous 

 ramuscules unite, and give rise to a considerable trunk — the vena supra-renalis — on 

 which the organ is placed as on a pedicle. It is this vein wliich constitutes the 

 debated cavity.) 



The veins are satellites of the arteries in the tissue of the organ, and pass into 

 the renal vein or posterior vena cava. The lymphatics are scarce. 



The supra-renal bodies receive many ganglionic nerves derived from the solar 

 plexus, but their mode of termination is unknown. (As mentioned by Chauveau, 

 the nerves of these organs are extremely numerous, they being more abundantly 

 supplied than any other structure of the kind in the body ; a large number of 

 small branches enter the cortical portion, to become developed in the medullary 

 tissue. As these nerves do not leave the medullary substance, and as, besides, its 

 cellular elements appear to be of the same nature as the multipolar ganghonic 

 cells, it is presumed that the nerve-fibres emerge from these globules, and that 

 the medulla acts as a ganglionic nerve centre. Though Leydig fully believed 

 the internal portion to be of a nei-vous character, he thought another function 

 might be attributed to the cortical, in consequence of its being most frequently 

 of a fatty nature. Bergmann was the first, in 1839, to class these organs with 

 the nervous system, and Remak, in 1847, by his researches in embryology, was led 

 to group them with the sympathetic ganglia, and named them nerve-glands. 

 Injm-y to the dorsal portion of the spinal cord, causes congestion and hypertrophy 

 of the supra-renal capsules. In a watery solution of the cortical portion, a rose- 

 tinted substance has been discovered, which changes to green with persalts 

 of iron.) 



Development. — These bodies are relatively larger in the foetus than the adult, 

 though this difference does not influence their structure. 



(Functions. — Their uses are still unknown ; they are ranked in the category 

 of blood-vascular glands, along with the spleen and thyroid body, the functions 

 of which are also not yet ascertained. Leydig is of opinion that these bodies 

 should be regarded as belonging to the nervous system ; but it is probable that 

 they are concerned in the processes connected with pigmentation.) 



Differential Characters in the Urinary Apparatus of the other Animals. 



1. Kidneys. — In the other domesticated Mammals, the renal glands are simple or multiple, 

 or, in other words, simple or lobulated. In the Ox, the kidneys liave an elongated shape 

 from before to beliind, which is altogether characteristic; and, in addition, they preserve 

 during life the lobulated form only seen in the other animals during intia-uterine existence. 

 Each agglomeration is composed of from fifteen to twenty secondary kidneys ; but the pelvis 

 is not formed in the centre of this agglomeration, being carried altogether outwards, and 

 occupying an excavation in the interior face of the organ, which represents the hilus. This 

 cavity is divided into as many short, wide prolongations — the calices — as there are principal 

 lobules ; the uriniferous tubes from each lobule open on a small papilla, which projects into 

 the bottom of the calyx. This papilla is, therefore, nothing more than the crest of the simple 

 pelvis in tlie kidney of Solipeds (Fig. 347). 



In the Sheep and Camel, the kidneys are not lobulated, and the pelvis is carried to the 

 inner border, as in the Horse. In these animals, as well as in the Dog and Cat, there is an 

 arrangement which establishes a kind of transition between the pelvis of the Ox and that of 



