THE UBINJBY APPABATUS. 495 



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 ganglionic cells, it is presumed that the nervous 

 fibres emerge from these globules, and that the medulla acts as a ganglionic 

 nervous centre. Though Leydig fully believed the internal portion to be 

 of a nervous 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 Eemak, in 1847, by his researches in embryology, was led to 

 group them with the sympathetic ganglia, and named them nervous glands. 

 Injury 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 difierenoe 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, 

 whose functions are. also not yet ascertained. (Leydig is of opinion that 

 these bodies should be regarded as belonging to the nervous system.) 



DIPFEKENTIAL OHABACTEKS IN THE UKINAKY APPAKATUS OF OTHER THAN SOLIPED 



AKIMALS 



1. Kidneys. — In other than Soliped animals, the renal glands are simple or multiple, 

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

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

 preserve during life the lobulated form only seen in the other animals dm-ing intra- 

 uterine existence. Each agglomeration is composed of from fifteen to twenty secondary 

 tidneys ; but the pelvis is not formed in the centre of this agglomeration, being carried 

 altogether outwards, and occupying an excavation in the inferior i'ace 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 m-iniferous 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 the kidney of Solipeds (Fig. 256). 



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

 border, as in the Horse. 



The kidneys of the Pig are simple and voluminous, and their pelvis is disposed as in 

 the Horse. (There are 10 or 12 papillae, and as many calices.) 



In the Dog and Cat, there are no calices absolutely comparable with those of 

 Ruminants. The pelvis is simple, and presents at the bottom a single, large, elongated 

 tubercle, that has at its base some very short projections or pillars. 



2. Bladder. — The most important difference in the bladder of the domesticated 

 animals consists in the extent of the development of its peritoneal envelope. In non- 

 soliped animals this covers all the organ to the neck ; the ligaments are also very short, 

 and the viscus may be easily projected into the abdominal cavity. The bladder is thin, 

 and of a considerable capacity in Buminants and the Pig ; in the Dog, on the contrary, 

 it has a very thick muscular layer, its fibres forming distinct fasciculi, especially when 

 in a state of retraction. (In Ruminants, the orifices of the ureters are near each other ; 

 at the fundus the mucous membrane shows a small fossa which is continued by a narrow 

 canal that terminates iu a cul-desac, and constitutes a free appendix about half an inch 

 long, and of the thickness of a goose-quill.) 



3. Supra-renal capsules. — These small organs are discoid in the Sheep and Pig, 

 reniform in the Dog. In the Ox, they are situated at a certain distance in front of the 

 kidneys, and their shape is like that of these bodies in the Horse; though they are a little 

 constricted in the middle, and slightly curved. 



In Birds, the kidneys " are lodged at the same height, behind the peritoneum, 

 immeiliately posterior to the lungs, and in the lumbar and pelvic regions, where they 

 occupy several fossse excavated in the upper face of the pelvis. Their form is irregular 

 and more or less elongated, depending upon the bones and other parts to which they are 



