TUMORS AFFECTING CATTLE. 



By John R. Mohlek, V. M. D., 

 Chief, Bureau of Animal Industry. 



[Synoni/nis: New growth, neoplasm, ueoformatiou, pseudoplasm, swelling, and 

 hyperplasia.] 



Definition. — Tumors ^ are abnormal masses of tissue, noninflamma- 

 tory and independent in character, arising, without obvious cause, 

 from cells of preexistent tissue, possessing no physiologic function, 

 and characteristically unrestrained in growth and structure. 



Tumors are abnormal masses of tissue. The aijplication of the 

 term " tumor " is directly connected with the fact that they produce 

 local enlargement. 



They are noninflammatory; that is, the process of inflammation is 

 not directly the cause or accompaniment of them. An inflammatory 

 new growth tends to disappear upon the subsidence of the inflamma- 

 tory process, while spontaneous disappearance of a tumor is compar- 

 atively rare. 



Tumors are independent. For instance, their nutrition bears no 

 relation to the nutrition of the body. A lipoma, or fatty tumor, in 

 the subcutaneous tissue, may go on increasing to huge bulk while the 

 body is steadily emaciating. Again, the tissues of the aged gradually 

 undergo atrophy, yet cancers arise at this time and grow rapidly. 



Tumors are unrestrained in growth and structure. In the develop- 

 ment of an animal we know at what period of its existence the mass 

 of tissue called liver will develop — what its site, structure, and size 

 will be. We know that it will remain only in that locality, and not, 

 as it were, colonize throughout the system. With tumors it is differ- 

 ent; there are no laws by which we can forecast the time, place, 

 nature, or size of development of them. There is no cartilage in the 

 kidney or parotid gland, yet a chondroma, or cartilage tumor, may 

 develop in either. Even when a new growth of tissue is started by 



^The term " tumor" literally means a swelling, and thus has been applied to the promi- 

 nence caused by an overdistended bladder, to the enlargement of pregnancy, to the swell- 

 ing produced by an abscess, to the overgrowth of tissue (.hyperplasia) associated with 

 Injury and consequent inflammation, and to numerous other phases of tissue enlargement 

 directly connected with recognized disease processes. For this reason it is becoming more 

 common for scientists to apply the word " neoplasm " to the new growths described in 

 this chapter. Because of the still popular use of the word " tumor," it is retained in this 

 chapter for the designation of those new growths to which the sevenfold characterization 

 of our descriptive definition applies. 



303 



