182 STRUCTURE OF CANCER. 



itself to communicate the disease to that part ; more- 

 over cancer can be conveyed from one animal to another, 

 both by inoculation and the injection of the cancerous 

 matter into the veins : a further proof of its par;i 

 origin. But although cancer is capable of being thus 

 transplanted from one individual to another, it occurs 

 in almost all cases under circumstances in which it is 

 diilicult to believe that any such im -dilation ur infection 



taken place: the most common being from I 

 direct injury, or prolonged pressure and irritation of 

 some part of the body. 



Thus c.mcrr of the jiicntlv ascribed I 



blow ; r of tin- lip to the constant pressure of 



a pipe ; cancer of the penis to c ! phym- 



can<vr of tin- anus and reetum to piles or syphilitic 

 vegetatio! <T of i! >, to the 



irritation of soot, &c. 



These few instances go to hear out the old dod : 

 that a dis-a>e not primarily malignant m. 

 a (i' gree at \ with 



the theory that : is of can- intro- 



duced from without. The s' 



additional reasons for reje- that the g- 



of tin always intrmluc.-d IV.. m without. 



essential elements of can of othei 



nucleated cells and tihn I multiph 



tin-owing off the germs of IV- from ti. 



surface ; and son from their innei 



as in the Colloid form of the disease. 



All these circumstances go to prove tlia: 

 originates in a depraved nutrition of the ori_ 

 nucleated cells of the part in which it lii>t app- 



