PART 2.— THE SENSITIZING PRINCIPLE. 
THE EFFECT OF HEAT UPON THE SENSITIZING ACTION OF 
HORSE SERUM. 
In previous publications we reported that the toxic action of horse 
serum was not destroyed when the serum was heated to 60° C. for six 
hours, but is entirely destroyed at 100° C. in fifteen minutes. Further 
work on this subject leads us to conclude that the sensitizing effect 
of horse serum is gradually influenced by heat, and almost entirely 
disappears when the serum is heated to 100° C. for one hour. 
The pigs sensitized with small quantities of horse serum heated to 
100° C. for one hour, when subsequently tested, developed veiy slight 
symptoms. 
Table No. 5. — Effect of heat upon sensitizing principle. 
Result. 
Very severe symp- 
toms. 
Slight symptoms. 
Dead in 4 minutes. 
Marked symptoms; 
died 2 days later. 
Severe symptoms. 
Mild symptoms. 
Severe symptoms. 
Severe symptoms. 
No symptoms. 
No symptoms. 
Dead in 90 minutes. 
No symptoms. 
Marked symptoms. 
( 11 ) 
G.P. 
No. 
First injection. 
Inter- 
val in 
days. 
Second injection. 
1193 
Heated to 60° C. 
0.02 c. c. normal horse (roan) 
25 
0.25 c. c. nonnal horse (roan) ^ 
1194 
serum, diluted 1:3 with dis- 
tilled water and heated 60° 
for 1 hour, subcutaneously. 
Heated to 70° C. 
0.02 c. c. normal horse (roan) 
25 
serum into brain. ; 
6 c. c. normal horse (roan) se- 
1195 
serum, diluted 1:3 with dis- 
tilled water and heated 70° 
for 1 hour, subcutaneously. 
25 
rum intraperitoneally. 
0.25 c. c. normal horse (roan) 
1197 
Heated to 80° C. 
0.02 c. c. normal horse (roan) 
25 
serum into brain. 
6 c. c. normal horse (roan) se- 
1190 
serum, diluted 1:3 with dis- 
tilled water and heated 80° 
for 1 hour, subcutaneously. 
do 
1 
25 
rum intraperitoneally. 
0.25 c. c. normal horse (roan) 
i 
3242 j 
1 
39 
serum into brain. 
6 c. c. normal horse (roan) se- 
! 
3244 i 
do. 
39 
rum intraperitoneally, 
do 
3240 
do 
39 
do 1 
1199 
Heated to 90° C. 
1 
0.02 c. c. normal horse (roan) 
25 
i 
1 
1198 
j serum, diluted 1:3 with dis- 
tilled water and heated 90° 
for 1 hour, subcutaneously. 
25 
0.25 c. c. normal horse (roan) 
3238 
39 
serum into brain. 
6 c. c. normal horse (roan) se- 
3235 
do 
39 
rum intraperitoneally. 
do 
3239 
do 
■ 39 
do 
