30 
The experiments with whole milk which was heated to 170° C. 
for ten minutes certainly seem to show that the effect of heat depends 
upon the coagulability of the protein; for, as is well known, fresh 
milk (not acid) may be heated to high temperature without causing 
coagulation of any appreciable amount of the protein, whereas if 
undiluted serum or egg white be heated to temperatures above 60° 
C. they are coagulated. 
We agree with Wells in believing that this is due entirely to the 
fact that the proteins of serum and egg white are rendered insoluble 
by heating, whereas those of milk are not affected. 
THE EFFECT OF HEAT UPON THE SENSITIZING PROPERTY OF 
PROTEINS. 
We and others have reported that the sensitizing property of serum 
is gradually affected by heating to temperatures above 80° C. until 
practically destroyed at 100° C. for one hour. 
We now wish to report some further work on the effect of heat 
upon the sensitizing properties of proteins. In these experiments 
the various proteins used were first dried and then heated to different 
temperatures, subsequently redissolved, and used to sensitize guinea 
pigs. 
As will be seen from Table No. 16, dried horse serum may be heated 
to 130° C. for two hours, 150° C. for ten minutes, or 170° C. for ten 
minutes, without impairing to any appreciable degree its sensitizing 
properties. 
Likewise, milk may be dried, then heated to temperatures varying 
from 130° C. for two hours to 170° C. for ten minutes, redissolved, 
and found to be as potent for sensitizing as the unheated milk. Also, 
the fluid whole milk may be heated to 130° C. for fifteen minutes or 
170° C. for ten minutes without altering its sensitizing properties. 
Egg white when dried, either whole or purified, may be heated to 
the same high temperatures without apparently altering its ability 
to sensitize guinea pigs to a subsequent injection of the unheated 
protein. 
Table No. 16. — Sensitizing action. 
HEATED DRIED SERUM. 
1 
G'. P. No. 
1 
G. P. | 
i weight. 
First injection. 
Inter- 
val in 
days. 
Second injection. 
Result. 
1 
0.01 c. c. saturated solu- ! 
tion of dried antitetanic 
horse serum heated to 
150° C. for 10 minutes ! 
and redissolved, sub- 
cutaneously. 
j 6c. c. normal horse (Frank) 
serum, intraperitoneally. 
Very severe symp- 
toms. 
