270 



VETERINARY PATHULUGV. 



tumors. They are, in some cases at least, a result of peripheral 

 extension and development of the tumor tissue around normal 

 nerve tissue, thus entangling it in the tumor. It is an open 

 question whether nerve tissue exists in tumors except in those 

 derived from normal nerve tissue or those in which normal 

 nerve tissue is entangled. 



Leucocytes are common in tumors. Lymphocytes and poly- 

 morphonuclear leucocytes have been demonstrated in the blood 

 and lymph channels, perivascular and intercellular spaces, and 

 within the tumor cells. The cells and the manner in which they 

 are assembled, the structure and arrangement of the intercellu- 

 lar substance, and the presence of the blood and lymph vessels 

 indicate a common origin of tumor tissue and normal tissue. 



Fiy, 137. — Section of Sarcoma, showing saroonnatous crlls and blood vossrls. 



Size. — Tumors are quite variable in size. They ma^- l)ecome 

 so large that they mechanically destroy life. An abdominal sub- 

 serous lipoma, about the size of a wash-tub and weighing thirty- 

 eight kilograms, (S3i/;, lbs.) was observed in an ox. A six- 

 kilogram (13 v.", lbs.) fibroma was removed from the inferior 

 cervical region of an eighteen kilogram (40 lbs.) dog. A twelve 



