CHAPTER XV. 



TUMORS. 



DEFINITION.— Formerly the word "tumor" was used 

 as the universal designation for all enlargements and pro- 

 jections on the surface of the skin or subcutaneous connec- 

 tive tissue, which circumstance accounts for the application 

 of the word to abscesses, phlegmons, hernias, cysts, 

 haematomata, aneurisms, etc. Gradually, with the progress 

 of medicine and surgery, the different abnormal tumefac- 

 tions were properly distinguished from one another, and as 

 a result the sense of the word was restricted to enlargments 

 accompanied by the formation of new tissue. This concep- 

 tion, although more appropriate than that which had pre- 

 vailed before, was not entirely satisfactory because certain 

 inflammatory pathological processes combine in the forma- 

 tion of new tissue that is absolutely different from the genu- 

 ine neoplasm. Nowadays, only masses of new formation 

 that have a tendency to increase or persist independently 

 of all inflammatory processes, are regarded as tumors. This 

 view, although criticised and open to criticism, is, as a mat- 

 ter of fact, quite generally admitted as logical, and may as 

 well be maintained until new investigations, — some of 

 which have already shed new light on the subject, — remove 

 the majority of tumors considered as pure neoplasms from 

 this category. [For an anatomo-pathological and historical 

 study of tumors the reader is referred to works on General 

 Pathology, as only their clinical aspects will be considered 

 here. 1 



FREQUENCY. — Tumors are not rare among domestic 

 animals. Named in a scale of decreasing frequency the do- 



562 



