UKO-GENITAL SYSTEM 191 



as irregular, incapsulated masses, usually involving only one kidney, 

 and in size vary from five to fifteen pounds. Although they have 

 not been recognized clinically, their structure and appearance evi- 

 dence rapid growth. They have their origin in the kidney substance 

 near the pelvis, and the tumor tissue produces pressure atrophy of 

 the renal parenchyma. The outline of the tumor is irregular and 

 frequently lobulated. On being sectioned, fibrous bands are found 

 extending in various directions and dividing the tumor mass into 

 lobes. The neoplastic tissue is of a white or dirty-white color, but 

 is often mottled, due to hemorrhage; there may also be grayish- 

 yellow centers of necrosis. Microscopically, these tumors are com- 

 posed of embryonic epithelium and connective tissue, the epithelium 

 disposed as irregular tubules or remnants of tubules, while the cou- 

 ncLtive tissue occurs around and between the epithelial tumor cells. 

 Sometimes larger areas of embryonic connective tissue cells are found 

 independent of epithelium, and again the epithelium may occur in 

 nests in the sarcomatous tissue. 



The time for growth of these tumors has not been determined, but 

 they are most frequently found in swine less than two years of age. 



Sarcomas have also been encountered by veterinary inspectors in 

 the kidney of swine. They are usually metastatic, although one case 

 of a primary, large-spindle celled sarcoma has been recorded. 



Ureters 



MALFORMATIONS 



Malformations of the ureters are not uncommon, but the malfor- 

 mations that are observed are not of such a nature that the function 

 of the organs is interfered with and therefore are of no practical 

 importance. 



Eenal pelvic calculi may become lodged in the ureters and es- 

 tablish' inflammatory disturbances, and also obstruct the lumen. 



The ureters are subject to injuries in spaying and other abdominal 

 operations. 



Bladder 



MALFORMATIONS 



Malformations of the bladder are not common. A few cases of 

 double bladder have been recorded, or the bladder may be very small, 



