TUMORS AFFECTING CATTLE. 307 



seem to overlap. It is here that the microscope, as the court of last 

 appeal, adjudicates positively in the diagnosis between these two 

 clearly marked divisions. 



It may almost be asserted that a true classification of tumors can 

 not be made until we know more about the cause of them. The 

 arrangement here presented is offered to meet the practical needs of 

 the veterinarian, student, and farmer rather than of the pathologist. 



We may roughly divide the tissues of the body into structural and 

 lining tissues. The structural tissues are composed of the tissues of 

 special function and simple connective tissues. The lining or cover- 

 ing tissues, both internal and external, are known as epithelium. 



Section A of the table below contains the true tumors or proper 

 neoplasms. 



Section B includes the cysts, some of which are true tumors, while 

 others are false ones, but the latter are added because of their gross 

 resemblance to the true and the consequent necessity of considering 

 them at the same time. 



TUMORS AND CYSTS. 



A. — Tumors. 



BENIGN. 



I. — Tumors composed of tissues resemhling those of special function. 



1. Type of muscle tissue Myoma. 



2. Type of nerve tissue Neuroma. 



3. Type of vascular tissue Angioma. 



4. Type of gland tissue Adenoma. 



II. — Tumors composed of fuUy developed connective tissue. 



1. Type of fibrous tissue Fibroma. 



2. Type of adipose, or fat, tissue Lipoma. 



3. Type of cartilage tissue Chondroma. 



4. Type of osseous, or bone, tissue Osteoma. 



5. Type of neuroglia, or nerve, sheath Glioma. 



0. Type of mucoid, or mucous, tissue Myxoma. 



MALIGNANT. 



III. — Tumors composed of emhryonic or immature connective tissues. 



1. Type of immature connective tissue Sarcoma. 



2. Type of endothelial tissue Endothelioma 



IV. — Tumors in which epithelial elements predominate. 

 1. Type of various epithelial cells and associated tissues Carcinoma. 



