318 DISEASES OF CATTLE. 



this chapter depends chiefly upon its practical character, which in 

 turn is measured by its aid in diagnosis, prognosis, and treatment, 

 the old but important clinical division is here adopted. 



Tumors are either malignant or benign. The essential difference 

 between the two classes is that while benign tumors depend for 



THEIR ILL EFFECTS ENTIRELY UPON THEIR SITUATION. TMALIGNANT 

 NEOPLASMS AVHEREVER LOCATED INEVITABLY DESTROY LIFE. The 



clinical features of each group are in many cases sufficiently marked 

 to distinguish them. 



MALIGNANT TUMORS. 



(1) These are invariably pernicious and from the beginning tend 

 to destroy life. 



(2) The cellular element predominates, therefore they grow 

 rapidly. 



(3) Possessing no capsule, they infiltrate surrounding tissues. 



(4) They infect adjacent lymph glands. 



(5) They recur even after complete removal. 



(6) They give metastasis; that is, they become disseminated in dif- 

 ferent organs. 



(7) Their presence develops a progressive emaciation. 



BENIGN TUMORS. 



(1) These in and of themselves do not tend to produce death. 



(2) As the cellular element is not apt to predominate, they grow 

 slowly. 



(3) They are encapsulated, and when diffuse do not infiltrate sur- 

 rounding tissues. 



(4) They do not infect adjacent lymph glands. 



(5) They do not recur after complete removal. 



(6) They do not manifest metastasis. 



Benign tumors, though hannless, may, by the accident of their 

 location, indirectly produce death. Mere pressure on the brain sub- 

 stance of an otherwise innocent tumor, compression of the blood sup- 

 ply for vital organs, growth in such manner as to cause obstruction 

 in the alimentary tract or pressure upon nerves, may cause death, or, 

 prior to death, so combine the effects of anemia (deficiency of blood), 

 starvation, and pain, with its consequent restlessness, as to produce a 

 veritable cachexia. 



On the other hand, a malignant tumor in its primary growth may 

 so implicate a vital organ as to destroy life before metastasis can 

 occur or even before cachexia can develop. Thus, to the untrained 

 observer, environment may so operate as to cause these two classes 



