BOOK IV. 



THE URINARY APPARATUS. 



This apparatus, though simple, yet plays a very important part in the animal 

 economy, as it is charged with the duty of eliminating from the blood — along 

 with the superfluous water and other accessory substances — the excrementitial 

 nitrogenous products resulting from the exercise of the vital functions. These 

 products we find in the urine —the liquid secreted by the kidneys, and which 

 is carried by the iireters into a special reservoir— the bladder — where it accumulates, 

 and whence it is expelled from the body by the urethral canal, at periods more or 

 less distant, according to the requirements of the animal. 



The kidneys, the essential organs of urinary depuration, will be first studied ; 

 then the excretory apparatus ; and, finally, a brief notice will be given of the 

 supra-renal c«jt?sM/es— small bodies annexed to the kidneys, the function of which 

 is not yet determined. 



Preparation. — Place the animal in the first position, and remove one of the posterior limbs. 

 Take out the intestines, adopting the precautions indicated at page 455. Saw througli the 

 pelvic symphysis, as well as the neck of the ilium on the side opposite the remaining abdominal 

 limb, removing the coxal portion between these sections. The pelvic cavity being now 

 opened, the urinary apparatus is exposed, and to complete the preparation it is necessary to : 

 1. Remove the peritoneum, to show that the urinary apparatus is situated external to that 

 membrane. 2. Free the ureters and kidneys from the cellulo-adipose tissue surrounding them, 

 but retaining the vessels of the latter, and leaving undisturbed their relations with the pan- 

 creas and supra- renal capsules. 3. Inflate the bladder, and dissect its neck, taking care to 

 preserve the orbicular peritoneal fold which envelops its anterior cul-de-sac (or fundus). 



In the male, the inflation of the bladder is very simple, and requires no directions. In the 

 female, however, it is requisite first to close the meatus urinarius, which is accomplished by 

 drawing its two lips towards the entrance to the vulva, by means of two chain-hooks, passing 

 two pins through their mucous membrane, and tying a ligature behind these ; the bladder is 

 then inflated by the ureter. 



Independently of this dissection in situ, it is advisable to examine the urinary apparatus 

 when isolated, and laid arranged upon a table, as in Fig. 338. We can then study : 1. By 

 dissection, the structure of the kidneys and arrangement of the pelvis reualis. 2. The mode of 

 termination of th« ureters. 3. The interior of the bladder. 



1. The Kidneys (Figs. 258, 338). 



Situation. — These are two glandular organs situated in the abdominal cavity, 

 to the right and left of the sublumbar region, lying against the great psoas 

 muscles, and maintained in that position : 1. By an envelope of cellulo-adipose 

 tissue. 2. By the peritoneum, which passes beneath them. 3. By the pressure 

 of the digestive organs contained in the abdominal cavity. 



Their situation is not absolutely alike, for the right comes forward to beneath 

 the two last ribs, while the left scarcely reaches beyond the eighteenth rib. The 

 latter is, therefore, more posterior than the former. 



External conformation. — Studied externally, the kidneys present a special 



