Vol. 6, 1920 
PATHOLOGY: J. B. MURPHY 
37 
EXPERIMENT NUMBER 
II 
III 
AVERAGE 
Takes in heated mice . 
Takes in control mice 
Number of mice used . 
30.0% 
77.8% 
20 
30.0% 
78.8% 
33 
50.0% 
94.5% 
54 
Total 107 
36.6% 
83.6% 
The effect of heat stimulation was also tested on the resistance of mice 
with spontaneous tumors to replants of their own cancers. The result 
in this case was even better than that obtained with the small doses of 
X-rays. The heated mice had an immunity of 59.4% as compared with 
50% in the X-rayed series and 3.4% in the untreated animals. 
It will be noted that in our experiments with the transplanted tumors 
we made our transplantations one week after exposure to the heat or the 
X-rays. This time was selected at first because the greatest stimulation 
occurred then. Further experiments indicated that if animals treated 
by either of these methods were inoculated during the first two or three 
days after treatment there was either no immunity or very slight evidence 
of it. The following table illustrates this point : 
This observation offers a very interesting parallel with that on immunity 
induced by tissue injection. The immunity is non-operative during the 
first few days and is at its best between seven and ten days after the in- 
jection. It seems to me of considerable interest that we are able to in- 
duce the same degree of immunity by the use of physical agents as by the 
use of what we may call a biological agent. The points in common are: 
the lymphocytosis induced by the physical agents, which occurs normally 
after the use of the biological agent, and the latent period before the im- 
munity, become evident after the use of all three of the agents. 
Summary. — It was first shown that animals immune to transplantable 
cancer showed a large increase in the circulating lymphocytes after cancer 
inoculation. This reaction is accompanied by hyperactivity of the lym- 
phoid tissue of the spleen and lymph nodes. If the reaction is prevented 
by the destruction of the lymphoid tissue the immunity is destroyed, and 
the animal becomes susceptible to cancer inoculation. 
Two methods have been found whereby the lymphocytes may be 
markedly increased along with a heightened activity of the germinal 
lymphoid centers: (1) by exposure to diffuse, small doses of X-rays; and (2) 
by exposure to dry heat. The lymphocytosis and lymphoid hyperplasia 
induced by these two physical agents are associated with an immunity to 
transplanted cancer equally as great as that arising from tissue injections. 
AVERAGE 
Takes in mice X-rayed 1 week before inoculation 
Takes in mice X-rayed 1 to 3 days before inoculation 
Takes in control mice 
Takes in mice heated 1 v^^eek before inoculation 
Takes in mice heated 1 to 3 days before inoculation . . 
Takes in control mice 
36.6% 
77.7% 
86.2% 
27.7% 
60.0% 
67.0% 
