THE URO-GENITAL SYSTEM 



111 



rhage; there may also be grayish-yellow centers of necrosis. 

 Microscopically these tumors are composed of embryonic 

 epithelium and connective tissue, the epithelium disposed 

 as irregular tubules or remnants of tubules, while the 

 connective tissue occurs around and between the epi- 

 thelia tumor cells. Sometimes larger areas of embryonic 



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Fig:. 4. ADENO-SARCOMA OF THE KIDNEY. 



A. Normal kidney tissue. B. hemorrhagic areas. C. pelvis. D. sar- 

 comatus tissue. (This kidney was seven or eight times as large as 

 a normal kidney.) 



connective tissue cells are found independent of epi- 

 thelium, 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. 



