DISEASES OF CATTLE 431 



able ear. The only recourse for its removal is the knife in the hands 

 of one acquainted with the anatomy of the part involved in the 

 operation. 



TUMORS AFFECTING CATTLE. 



[Synonyms: New growth, neoplasm, neoformation, pseudo- 

 plasm, swelling, and hyperplasia.] 



Definition. Tumors* are abnormal masses of tissue, nonin- 

 flammatory and independent in character, arising, without obvious 

 cause, from cells of pre-existent tissue, possessing no physiologic func- 

 tion, and characteristically unrestrained in growth and structure. 



Tumors are abnormal masses of tissue. The application 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 inflammatory process, while spontaneous disappearance of a 

 tumor is comparatively 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. 

 They are unrestrained in growth and structure. In the development 

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

 sue 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 different; 

 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 an injury 

 and consequent inflammation as, for instance, proud flesh there is 

 a limitation of its size. But the controlling influences which govern 

 the size of an organ or normal mass of tissue and limit the extent of 

 an inflammatory overgrowth are all absent in the case of tumors. 



Tumors arise without obvious cause. Concerning the ultimate 

 cause of tumor formation we are absolutely ignorant. Various theo- 

 ries have been advanced from time to time, but none of them have 

 been applicable to more than a limited number of cases. 



Diagnosis. In the diagnosis of tumors note is taken of clinical 

 history and examination of the tumor. 



*The term "tumor" literally means a swelling, and thus has been applied to 

 the prominence caused by an overdistended bladder, to the enlargement of preg- 

 nancy, to the swelling produced by an abscess, to the overgrowth of tissue (hyper- 

 plasia) 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 tho 

 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. 



