PRESIDENTIAL ADDRESS. 95 
fertile field to investigate is that of the nature of these, at 
present unknown, causes of chronic irritation. Such 
chronic irritation is so clearly a factor in so many forms 
of malignant growth that I feel it must play an equally 
important part in the majority of cancerous conditions. In 
this continent the money would be much better spent along 
these lines than in attempts to fathom the deeper meaning 
of the cancerous process—which, to my mind, is already 
solved. Of course this view carries with it the reservation 
that the researcher has not conceived some entirely new line 
of investigation that, to expert minds, carries with it the 
possibility of material advance in our knowledge of the con- 
dition. 
-Applying the above three factors to the case of rats and 
mice, we find that, as regards numbers, they are very abun- 
dant, and that for certain purposes (plague to wit) very 
many have come under close human scrutiny; that there 
is reason to think that a considerable number, in the ab- 
sence of epizootic disease and exposure to danger, reach an 
age that may be called old for them; and that, in one in- 
stance at least, a form of chronic irritation is known that 
is specially apt to lead to cancer. We would therefore 
expect to find cases of malignant growths amongst them 
during a systematic examination of a large number. In 
those coming under my notice in Australia, the following 
cases have been met with, viz.:—Amongst Epimys norvegi- 
cus, 11 cases; amongst #. rattus, 12 cases, and amongst 
Mus musculus, 3 cases. 
The following indicate the forms found :— 
In Epimys norvegicus: Squamous-celled epithelioma of 
the stomach.—August 30th, 1912. Associated with the 
presence of a round worm, at the time thought to be Pro- 
tosprrura muris (Spiroptera obtusa), but perhaps Gongy- 
lonema neoplasticum (which see for further details). 
