171 VETERIXARV I'ATHOLOGY. 



Consistency. — Some tumors are soft and spongy, jelly-like, 

 and from this type there are all variations up to those that 

 are hard and resistant, bone-like. Their consistency is determined 

 largely by the kind of tissue composing them and the secondary 

 changes (degenerations) that affect them. Myxomata being 

 largely composed of mucus are soft, iibromata are more resistant 

 and osteomata are bone-like. Chondromata are usually quite firm 

 and resistant, but they may undergo mucoid degeneration and 

 become soft and spongy. Colloid degeneration is rather common 

 in carcinomata, rendering them glue-like in consistency. O'cca- 

 sionallj- a tumor becomes calcified as a result of calcareous infil- 

 tration. 



Number. — Tumors ma}' be single, that is, a single one only 

 occurring in the animal body. Single tumors are usually benign 

 although thev mav be malign. An animal may be afflicted with 

 a great many tumors at th.e same time (multiple tumors). Tum- 

 ors may become multiple by metastasis. Tumors resulting from 

 metastasis are designated secondary and the original tumor pri- 

 mary. Alultiple tumors may be malign, as sarcomata, carcino- 

 mata, etc., or thev may be benign, as multiple fibromata. Tum- 

 ors tliat recur after they have lieen removed are designated recur- 

 rent tumors. 



Growth. — Tlie growth of tumors is the result of the inherent 

 pri iliferatn-e prnpcrlv of the tumor cells. Srime tumors grow like 

 an onion, there l^eing a multiplication and accumulation of the 

 central or internal cells, resulting in an interstitial expansion and 

 an increase in tlie size of the tumor. Practically all Ijenign tmn- 

 ors grov bv interstitial expansion. Malign tumors grow bv mul- 

 tiplication of the peripheral cells and their infiltration as well as 

 by interstitial expansion. The extent of growth of all tumors is 

 projiortional to the amoimt of nourishment they receive and to 

 the adjacent tissue resistance. The relative amount of nourish- 

 ment to tumor tissue and to normal tissue in the same bodv mav 

 be verv nnec|ual. Thus a tumor frequently receives an excessive 

 amount of nourishment and grows rapidly, while the normal tis- 

 sue in the same bodv is depri\-ed of nourishment, resultmg in its 

 atrophy or degeneration and emaciation. As a rule, the rate of 

 growth is indefinite. Malign tumors grow more rapidly than be- 

 nign. A tumor that is growing rapidly may cease growth, dim- 

 inish in size, grow again and diminish again. Diminution in 

 size may be succeeded by absorption and disappearance. 



Extension. — The manner of extension of the various tumors 

 depends upon the migratory properties of the tumor cells and 

 the relation and structure of the blood and lymph vessels. Turn- 



