SMALLPOX, SYPHILIS, CANCER, ETC. 183 



Cancer 



In pathology the term cancer is applied to a malignant 

 tumour which originates in epithelium such as the epidermis, 

 or mucous membranes such as the lining of the mouth, the 

 stomach, or bowel ; or the epithelial part of a gland such as 

 the liver. A sarcoma is a malignant tumour that originates 

 in one or other of the connective-tissues : fibrous tissue, 

 bone, &c. We may think of these two phases of disease as 

 epithelial cancer and connective-tissue cancer respectively. 



Cancer affords greater opportunities for investigation 

 than almost any other disease : its dread plenty, long 

 course, and the frequent calls for operation furnish material 

 only too abundant. Added to this the facility with which 

 cancer can be grafted into mice gives those who have sanction 

 opportunity for unlimited observations. Of the countless 

 experiments that have been made with Jensen's mouse 

 cancer the result obtained by Ehrlich and Apolant is the 

 most important : on transplantation epithelial cancer be- 

 came sarcoma, showing it cannot otherwise be explained 

 that the two diseases are one, and that both are caused by 

 the same parasites. 



Parasites of a Connective-tissue cancer. Photographs 

 of a sarcoma of the breast are reproduced in Fig. 53. A 

 detailed account of this tumour having been given in Part II, 

 only the chief features need be noticed here ; they demand 

 patient and minute attention. 



