PRINCIPLES OF VETERINARY SURGERY 51 



terrier breeds. It is very contagious and capable of being 

 communicated from dog to bitch, and vice versa, during cop- 

 ulation. Macroscopically, these tumors have a cauliflower 

 appearance similar to a soft papilloma. They begin as small 

 yellowish white raised patches, about the size of a mustard- 

 seed, growing into clusters of friable masses, which bleed 

 readily when touched. Microscopically all these tumors pos- 

 sess several distinct characteristics, which, however, are by 

 no means pathognomonic, being found also in sarcomata. 

 When seen under the low power of the microscope, these tu- 

 mors present the appearance of a round-celled sarcoma, or an 

 endothelioma, but they have a thin covering of stratified 

 squamous epithelium. Under the higher power, the tumor- 

 cells have the appearance of embryonic connective tissue 

 cells in every stage of growth. Many are small round-cells 

 with a vesicular nucleus. Mitosis can be seen in many of the 

 cells. Some of these cells are spindle-shaped, and others 

 fusiform, while many typical branched cells — the fibroblasts 

 — are present. There is usually a leucocytic infiltration. In 

 some of Dr. C. A. White's cases, a characteristic endotheli- 

 oma could be seen. The endothelial cells can be seen spring- 

 ing from the endothelial lining of the blood-vessels, and occa- 

 sionally epithelioidal cells are present. 



Some pathologists classify these tumors as true sarco- 

 mata, others as infectious granulomata, but recent investi- 

 gations by Reitman and Amadon would suggest that these 

 are true mycotic tumors of an infectious nature. 



