Sarcoma. 371 



with the rapid exuberance of th? celhilar growth, various retro- 

 grade metamorphoses are possible, of which fatty degeneration is 

 the most common. 



Nothing certain is known of the development and cause of origin 

 of sarcomata. Now and again sarcomata and their combined 

 growths are met following traumatism (fractures of bone, contu- 

 sions and injuries to the soft parts) ; from the analogy shown by lux- 

 uriant traumatic granulation tissue growth to the sarcomata, it may 

 be supposed that some instances are due to lesions causing loss 

 of tissue tension, and further investigation of convincing ex- 

 amples would be of much interest in this line. In the second place 

 sarcomata may be thought of as perhaps related in their origin with 

 faults of development, both because they are common in man and 

 animals in early life and because their cellular character is sugges- 

 tive of embryonal conditions. 



The principal seats of primary sarcoma formation in animals 

 are the bones (jaw in dogs and horses, cranial cavity in cattle), the 

 lymphatic glands and spleen (dogs, cattle), and the intestine (cat- 

 tle) (Frohner, Leisering, Dieckerhoff, Siedamgrotzky, Casper). 



[Of the sarcomas it may be said in a general way, to which ex- 

 ceptions are not infrequent, that the spindle cell varieties more 

 commonly arise from the denser types of connective tissue as the 

 periosteum, fasci?e, intermuscular septa and capsules or framework 

 of organs ; and that the round cell forms more commonly originate 

 from the softer and more cellular types of connective tissue, as the 

 lymphoid structures and the intraparenchymatous intercellular con- 

 nective tissue of organs. The giant cell sarcoma is practically lim- 

 ited to the bone marrow, usually growing toward the ends of the 

 shafts of the long bones. 



In the same comprehensive way, again with many exceptions, it 

 may be expected that the round cell types are the larger, more irreg- 

 ular and more infiltrative as primary growths, and of a soft fleshy 

 consistence, highly vascular, and, before the blood has been washed 

 out, of a red, translucent, soft fleshy appearance (paler, as above de- 

 scribed, after the blood has been removed or if the growth when 

 obfained from the subject is relatively freed from its blood con- 

 tents) ; the spindle cell form tending in the same general and un- 

 fixed manner to be smaller in size, less infiltrative, but rarely encap- 

 sulated, more regular in outline and nodular or lobulated, somewhat 

 firmer in consistence and of a lighter color than the round cell varie- 

 ties. The giant cell sarcoma usually causes an expansion of the 

 bone shaft, is covered with a thin and generally imperfect shell of 



