MELANOSIS, OE MELANOTIC SAECOMA. 435 



round-celled sarcoma, the other forms already mentioned pre- 

 sent very little interest to the practical veterinarian, as they 

 are rar(3ly met with amongst his patients. The only case of 

 pure spindle-celled sarcoma that I ever had the opportunity of 

 examining was in a well-bred cow, whose cutaneous tissues 

 were covered with innumerable ulcerating tumours, having the 

 histological character of this form of sarcoma. 



MELANOSIS, OE MELANOTIC SAECOMA. 



Melanosis, described in the first edition of this work as black 

 cancer, is found, upon further investigation, to belong to the 

 sarcomata, or, as already stated, tumours consisting of embryonic 

 connective tissue. 



In structure the sarcoma consists of connective tissue, which 

 retains its embryonic characters and cells, and constitutes nearly 

 the whole of the growth. The round cells are those generally, T 

 may state, always found in the melanosis of the lower animals, 

 and are similar in form to white blood corpuscles, but containing 

 granules of dark pigmentary matter, which give the tumours 

 their characteristic black appearance. 



The dark granules of pigment not only fill the cells, but lie 

 free in the surrounding fibres, as shown in fig. 107 (c). 



Melanosis has hitherto been described as a benign disease in 

 the lower animals, both by human and veterinary pathologists. 

 Professor Spence says — "The melanotic cancer has this pecu- 

 liarity, that a form of it occurs in the lower animals which cannot 

 be distinguished from the black cancer in man. But in the 

 former case it is not malignant, and has no tendency to return 

 after removal, while in the human subject it is plainly and 

 entirely a malignant disease — a melanotic form of cerebriform 

 cancer." Paget says — " In the horse and dog, I believe, black 

 tumours occur which have no cancerous character; but none 

 such are recorded in human pathology." 



I have seen a great many cases of melanosis, but I never saw 

 one in the horse, the history of which I could afterwards trace, 

 where the disease did not return ; and if recurrence only were 

 the special characteristic of malignancy, this would prove the 

 true nature of the growth, without a shadow of doubt. But a 



