DISEASES OF THE UEINARY OEGANS. 117 



The kidney of the ox (PL IX, fig. 1) is a compound organ made up 

 of 15 to 25 separate lobules like so many separate kidneys, but all 

 pouring their secretion into one common pouch (pelvis) situated in 

 an excavation in the center of the lower surface. While 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 flattened from above 

 downward, and extending from the last rib backward beneath the 

 loins and to one side of the solid chain of the backbone. 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 latter, together 

 Avith blood vessels, lymph vessels, and nerves, make up the second, or 

 internal, layer. The outer layer is mainly composed of minute glob- 

 ular clusters of microscopic intercommunicating blood vessels (Mal- 

 phigian 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 ad- 

 vances 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 



