DISEASES OP THE BLOOD. 119 



local co-operation to combat them ; epizootics and pan- 

 zootics are of national importance. 



Cancer is a general term applied to tumours of a 

 malignant character. The tendency in the present day is 

 to restrict its use to the carcinomata^ which are new 

 growths of cells similar to epithelial, grouped irregularly 

 in a stroma. We shall give a detailed account of cancers 

 of various kinds later on, when treating of tumours. 



A 



M 



Fig. 20. — Elements of an Enceplialoid Tumour. 



Brown.) 



200. (After Harley and 



Certain forms of cancer have been successfully inoculated, 

 but great care is essential to success ; the morbid matter 

 must be directly transferred from one body to another, 

 and must be in a definite stage of activity. The process 

 reminds us of " grafting,^' and seems to indicate the 

 possibility, under certain circumstances, of cells differing 

 but little if at all in appearance from ordinary healthy 

 cells, acting as true contagia. In cases of cancer induced 

 by inoculation, the general constitutional disorder is an 

 effect of local conditions which seems to be the reverse of 

 the ordinary rule in specific affections. This exception is 

 rather apparent than real. In cancer the contagium must 

 attain local vigour and incorporation with the tissues 

 before it can involve the general mass of the blood. This 

 is not essential to any other known specific disorders 

 except, perhaps, scrofula and rabies. In examining a 



