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CHAPTER VII. 



Malignant Tumours. 



botktomtcosis scirrhous cord actinomycosis melanosis. 



The general meaning of a tumour is a " swelling." The most 

 readily observable characteristics of malignancy in a tumour are : 

 a tendency to recur if locally removed ; to extend to tissues other 

 than that in which it first appeared j and to invade distant parts. 

 These properties are of course absent in benign swellings, such as 

 splints, warts, and capped hocks. 



Botryomycosis 



is a diseased state of the tissues set up by the presence of special 

 micro-organisms, called discomyses equi, and also botryomyces. 

 They are often met with in scirrhous cord, poll evil, fistulous 

 withers, and in tumours which form on various parts of the 

 surface of the body. In all these cases, they appear to act as an 

 aggravation of an already existing wound, and not as an original 

 cause. It is probable that the Indian disease, bursatee, is due to 

 an allied parasite. The majority of fibrous tumours which have 

 suppurating sinuses, are due to botryomyces. These microbes are 

 found in fibrous tumours in the lungs, and the name of botryomy- 

 cosis has been given to the disease originated by them. It appears 

 that these parasites, like actinomyces, find a favourable residence 

 in decaying vegetable matter ; hence an objection to bedding-down 

 horses with open wounds (such as those inflicted by castration) on 

 peat moss, seems to be reasonable. The irri'tation caused by the 

 presence of this fungus, gives rise to a growth of fibrous tissue 

 which has a tendency to degenerate and break up in the form 

 of pus. 



