PRINCIPLES OF VETERINARY SURGERY 563 



mestic animals are classified as follows : Dog, cat, horse, ox, 

 small ruminants, and hog. All of the tissues, but especially 

 the mammae, the liver, the kidneys, the ovaries, the testicles, 

 the thyroid body and the lungs, are susceptible to neo- 

 plasms. Their importance varies with the nature and de- 

 gree of development. From the clinical point of view and 

 preceding the advent of the miscroscope, neoplasms were 

 divided into two great groups: ist. Benign tumors or those 

 which are compatible with life and comparatively good 

 health, and 2nd. malignant tumors, or those which provoke 

 disorders necessitating intervention. Tumors possessing 

 the following characteristics should be regarded as malig- 

 nant : 



1st. All tumors having a deep, diffuse implantation, 

 and which propagate by continuity of tis- 

 sue. 

 2nd. All tumors susceptible to generalization. 

 3rd. All tumors that recur after ablation. 

 4th. All tumors having cellular colonies that im- 

 pregnate the organism with products cap- 

 able of provoking cachexia. 

 When extirpated, the malignant tumor is usually found 

 aevoid of any membranous envelop or isolated capsule. 

 They are quite generally known by the name of "cancer," 

 and may attack every organ — the mucous membranes, the 

 liver, the pancreas, the kidneys, the prostate, the testicles, 

 the thyroid, the mamm^, the ovaries, the parotids, etc. 

 Out of 57 cages of malignant tumors Semmer found 32 sar- 

 comata and 25 carcinomata, and in further observations 

 found more cases of sarcomata. The following statistics 

 furnish a fair example of the relative frequency of the two 

 principal varieties of malignant growth in the different ani- 

 mals : 



