23 
rendering the proteins insoluble, rather than by the production of 
chemical changes in the protein. 
It occurred to us that perhaps this question could be conclusively 
settled by first drying the proteins, then heating them to the desired 
temperatures, redissolving them, and testing them for their toxicity 
upon sensitive guinea pigs. 
Dried serum can be heated to very high temperatures and subse- 
quently redissolved with, however, a slight loss in its power of going 
into solution. 
We dried horse serum, milk, egg white — both whole and purified 
egg white (the latter was kindly furnished us by Doctor Wells)— and 
heated them to varying degrees for different lengths of time, then 
redissolved them and tested the resulting solutions upon sensitive 
guinea pigs for toxicity. 
As will be seen from the table (No. 14), heating dried serum to 
130° C. for two hours or 150° C. for ten minutes, or 170° C. for ten 
minutes does not appreciably modify its toxicity for sensitive guinea 
pigs. 
Likewise, egg white, both whole and purified, may be heated to 
130° C. for two hours or 170° C. for ten minutes without appreciably 
affecting its toxicity. 
Milk, when dried, may be heated to 130° C. for two hours, 150° C. 
for ten minutes, or 170° C. for ten minutes, and found to be appar- 
ently more toxic than we have found the unheated milk. 
Likewise, whole milk may be heated to 170° C. for ten minutes or 
130° C. for two hours without any apparent decrease in its toxicity. 
It may be noted that when these dried proteins are heated to 130° 
for two hours or 170° for ten minutes they are slightly browned. 
Table No. 15. — Toxicity. 
HEATED- DRIED SERUM. 
G. P. No. 
G. P. 
weight. 
First injection. 
Inter- 
val in 
days. 
Second injection. 
Result. 
0.01 c. c. normal horse 
162 
6 c. c. of 4 per cent solution 
of dried antitetanic horse 
No symptoms. 
(Frank) serum, subcu- 
taneously. 
serum heated to 130° C. 
for 10 minutes, subcuta- 
neously. 
0.01 c. c. normal horse 
162 
6 c. c. of 4 per cent solution 
of dried antitetanic horse 
No symptoms. 
(Frank) serum, subcu- 
taneously. 
serum heated to 130° C. 
for 10 minutes, subcuta- 
neously. 
0.01 c. c. normal horse 
162 
6 c. c. of 4 per cent solution 
of dried antitetanic horse 
No symptoms. 
(Frank) serum, subcu- 
taneously. 
serum heated to 130° C. 
for 10 minutes, subcuta- 
neously. 
