•^na 



Maw 



596 



MARTIN — DISCUSSION ON CARCINOMA. 



that they invade denser tissues and infiltrate. Fibromata and other 

 benign tumours may remain untreated for years and their tendency 

 to invasion of other tissues is never manifest. They remain nearly 

 always localized, encapsulated, and cause injury only by mechanical 

 pressure. „ 



Th(5 ({uestion is rejvsonably luskcd as to why in the one case we get 

 metastases and not in the other, if a mere overgrowth of cells from 

 irritation or other non-parasitic causes will account for the origin of 

 both forms of tumours. The explanation cannot l)e ottered that the 

 nature of the individual cells of benign growtlis unfits them for trans- 

 mission by vessels, for when the varied nature and sizes of cancer and 

 sarcoma cells be considered it is not to be supposed that cells of other 

 tumours find greater difficulty in passing through the vessels. Again, 

 the mere fact that emboli of fat glt)bules can be; distributed over the 

 body after fractures, etc., and be found in the smallest capillaries of 

 the lungs would show that in one kind of tumour at least there is no 

 mechanical obstruction to the passage of its elements by vessels. 



There is further in malignant tumours not only a great activity, 

 but this activity is directed in a special w ly. It is a true invasion of 

 tissues — and invasion of vessel walls of all forms of tissues and by all 

 po.ssible channels. Wherever a distant part is infected with cells 

 froiii the original growth the process begins anew. 



So far as I ani aware there is no other pathological process apart 

 from parasitic attections possessing this same tendency of invasion 

 and extension. 



A further point of interest as illustrating the insufficiency of Cohn- 

 heim's theory as applied to malignant growths is obtained from a com- 

 parative study of tumours. Metchnikoff' has pointed out that in the 

 invertebrates cancer does not exist, while on the other hand it is very 

 probable t;..it cell renmants of epiblastic origin frecpiently oc* .n 

 this order of life, so that reasoning by analogy we are scarcely justi- 

 fied in attributing to such remnants the cause of cell proliferation in 

 malignant growths so far as vertebrates are concerned. 



To examme into the nature of malignant neoplasms it is in the fir.st 

 degree necessary that we should see if in other parasitic diseases we have 

 any evidence of new growths — it, in other words, parasites can induce 

 cell proliferations in any way analogous to cancers. Of this I think we 

 have abundant proof, and it will be of interest to institute a few com- 

 parisons between cancerous disease and those maladies where multiple 

 new growths occur from the invasion of the parasite. Prof. Coats 

 and others have asserted that an essential difference exists between 

 the lesions found in parasitic diseases and thosj occurring in cancer, 



