482 TUMORS 



size, and are seen as nodular collections under smooth skin. As a rule 

 lipomata are found on the tendons and their sheaths, the chest, shoulders, 

 and tail. Frohner found a lipoma that surrounded the anus in a half- 

 circle. Lipomata may be multiple but are not malignant. 



3. The Sarcoma. — A tumor made up of embryonic connective 

 tissue, originating in various parts of the body, such as cartilages, bones, 

 periosteum, adipose tissue, and in fact any of the connective tissues of 

 the body. Depending upon the size, shape and disposition of the com- 

 ponent cells, sarcomas are classified as small and large round cell, small and 

 large spindle cell, giant cell, melanotic and lympho-sarcomas. Sarcomas 

 are generally considered as malignant tumors (1) because they usually 

 show a tendency to become large, (2) because they are apt to reappear 

 after removal, and (3) because under certain conditions they are apt to 

 form in other parts of the body by metastasis. Their malignant char- 

 acter is generally much greater in proportion to the size of their cells 

 and the softer their intercellular substance. 



The external anatomical appearance of a sarcoma does not always 

 present characteristic symptoms. In most cases these tumors are round, 

 distinctly circumscribed, and sometimes they form encysted knots, which 

 vary in color and consistency. Their color depends, as a rule, on their 

 blood vascular supply, and any blood extravasations which may have 

 occurred also produce certain alterations, so that on section a sarcoma 

 may appear white, yellow, brown, gray, dark red, and even entirely black, 

 as the melanotic variety. This pigment sarcoma, or melanoma, is 

 extremely rare in the dog, although Gray asserts that it is very common 

 in Yorkshires, where it is seen in the form of small black excrescences 

 the size of a pea. Troutman describes an interesting melanosis of the 

 toe of a three-year-old setter. 



The metamorphoses which occur in the sarcoma are of some diag- 

 nostic value, especially the mucous softening, which leads to the forma- 

 tion of cysts and sometimes to bony deposits. This is frequently noticed 

 in sarcomas, and the ulceration of the adjacent skin and mucous mem- 

 branes occurs without producing any active disintegration of the tumor. 

 Notwithstanding the malignant character of the sarcoma, it may remain 

 in the same condition for years, and never inconvenience the animal, or 

 after lying quiescent for years it may suddenly begin to grow with 

 incredible rapidity. 



The myeloid or medullary sarcoma is a rare form of tumor which 

 grows in the marrow cavity of the bones. They have been noticed in 

 the forearm, shoulder-blade, arm, femur, maxilla and penis. Circum- 

 scribed nodules are developed in the medullary cavity which generally 

 crowd out the bone by their growth, and when new bone is formed from 

 the periosteum, fill up the entire cavity. In this manner we find enormous 



