318 VE'nCRINARV PATHOLOGY. 



These tumors may grow to an enormous size. The)- are not 

 as malignant as pure sarcomata and metastatic tumors are rare. 

 They should be differentiated from chondrofying sarcomata and 

 from sarcomata involving cartilage. 



Osteosarcoma. — This variety of tumors is composed of 

 osseous and sarcomatous tissues. The}' are rather common, 

 occurring in the horse, dtig and o.x. 



Microsco]5icalh', osteomatous and sarcomatous tissues are 

 arranged in various proportions and in various relations, but 

 the coml)ining tissue in any case must be new growth tissue. 

 (Jssifying sarcomata are not osteosarcomata, neither are sarco- 

 mata of osseous tissue osteosarcomata. 



These tumors are usually malignant, but they do not form 

 metastases. 



Hemangiosarcoma. — These tumors are composed of heman- 

 giomatous and sarcomatous tissues. They are relatively com- 

 mon, occurring in the location common for haemangiomata and 

 may affect any of the domestic animals. These tumors are essen- 

 tially very vascular and are higlily colored. 



In microscopic examination variations are observed in differ- 

 ent hemangiosarcomata. The sarcomatous tissue in some cases 

 appear to ha\'e liad its origin from the tunica adventitia of the 

 \esscl wall ; in other cases the sarcomatous tissue appears to 

 have had its origin independent of the vessels. Again, the ves- 

 sels may act as the supporting stroma for the sarcomatous tissue. 

 The \essels may be capillary or cavernous, sinusoid or plexiform. 

 The vessel wall may be ])ractically normal, but more frequently 

 it is either hypertrophied, as a result of increased numlier oj 

 the cellular elements or increase in the size of the cells, or it 

 may l)e thin, scale-like and atroi)hied. Sfjuietimes the endothe- 

 lial cells lining the vessels are cubic or columnar in shape, thus 

 diminishing the lumen of the vessel. The sarcomatous cells may 

 be either spindle-shaped or round. 



Tliese tumors are rpiite malignant, and they usuall\- grow 

 rapidly. The metastatic tumors are most frequently pure sarco- 

 mata. ,,',. 



PAPILLOMA. 

 (Wart.) 



Papillomata are fibro-epithelial tumors. These are perhaps 

 the most common of all tumors. They occur upon the surface of 

 the skin, and upon mucous, serous, and .synovial membranes. 

 They are very common upon the skin of calves, especially around 

 the eves, ears and poll. They occur most frequently on tlie lijis, 



