DISEASES OP THE URINARY ORGANS. 115 



the ox is the only domesticated quadruped which maintains this 

 divided condition of the kidney after birth, this condition is common 

 to all while at an early stage of development in the womb. The 

 cluster of lobules making up a single kidney forms an ovoid mass flat- 

 tened from above downward, and extending from the last rib back- 

 ward beneath the loins and to one side of the solid chain of the back- 

 bone. The right is more firmly attached to the loins and extends 

 farther backward than the left. Deeply covered in a mass of suet, 

 each kidney has a strong outer white, fibrous covering, and inside 

 this two successive layers of kidney substance, of which the outer is 

 that in which the urine is mainly separated from the blood and poured 

 into the fine microscopic urinary ducts. (PI. X, fig. 1.) These lat- 

 ter, together with blood vessels, lymph vessels, and nerves, make up 

 the second, or internal, layer. The outer layer is mainly composed of 

 minute globular clusters of microscopic intercommunicating blood 

 vessels (Malphigian bodies), each of which is furnished with a fibrous 

 capsule that is nothing else than the dilated commencement of a 

 urine tube. These practically microscopic tubes follow at first a 

 winding course through the outer layer (Ferrein's tubes), then form 

 a long loop (doubling on itself) in the inner layer (Henle's loop), and 

 finally pass back through the inner layer (Bellini's tubes) to open 

 through a conical process into the common pouch (pelvis) on the 

 lower surface of the organ. (PI. X-, figs. 1, 2, 3.) 



The tube that conveys the urine from the kidney to the bladder is 

 like a white, round cord, about the size of a goose quill, prolonged from 

 the pouch on the lower surface of the kidney backward beneath the 

 loins, then inward, supported by a fold of thin membrane, to open 

 into the bladder just in front of its neck. The canal passes first 

 through the middle (muscular) coat of the bladder, and then advances 

 perceptibly between that and the internal (mucous) coat, through 

 which it finally opens. By this arrangement in overfilling of the 

 bladder this opening is closed like a valve by the pressure of the 

 urine, and the return of liquid to the kidney is prevented. The blad- 

 der (PI. IX, fig. 2) is a dilatable egg-shaped pouch, closed behind by 

 a strong ring of muscular fibers encircling its neck, and enveloped by 

 looped muscular fibers extending on all sides around its body and 

 closed anterior end. Stimulated by the presence of urine, these last 

 contract and expel the contents through the neck into the urethra. 

 This last is the tube leading backward along the floor of the pelvic 

 bones and downward through the penis. In the bull this canal of the 

 urethra is remarkable for its small caliber and for the S-shaped bend 

 which it describes in the interval between the thighs and just above 

 the scrotum. This bend is due to the fact that the retractor muscles 

 are attached to the penis at this point, and in withdrawing that organ 

 within its sheath they double it upon itself. The small size of the 

 canal and this S-shaped bend are serious obstacles to the passing of a 



