8 
Table No. 2. — Period of incubation. 
G. P. 
No. 
First injection. 
Inter- 
val in 
days. 
Second injection. 
Result. 
1363 
0.01 c. c. normal horse serum 
1 
6 c. c. normal horse serum intra- 
No S5Tmptoms. 
into brain. 
perltoneally. 
1364 
do 
2 
do 
No symptoms. 
1365 
do 
3 
do 
No symptoms. 
1366 
do 
4 
do 
Suggestive. 
1367 
do 
5 
. ._do 
Suggestive. 
1368 
do 
7 
do 
Died in 25 minutes. 
1370 
do 
8 
do 
Suggestive. 
1369 
do 
9 
.. ..do 
Slight symptoms. 
1371 
do 
10 
. . do ... 
Dead in 35 minutes. 
1372 
do 
10 
6 c. c. normal horse serum sub- 
Mild symptoms. 
1 
cutaneously. 
Table No. 3. — Period of incubation. 
G. P. 
No. 
First injection. 
Inter- 
val in 
days. 
Second injection. 
Result. 
1423 
0.01 c. c. normal horse serum 
4 
6 c.c. normal horse senam sub- 
No symptoms. 
into brain. 
cutaneously. 
1424 
do 
4 
do 
No symptoms. 
1425 
. ..do 
5 
do 
No symptoms. 
1426 
do 
5 
do 
No symptoms. 
1428 
do 
6 
do 
No symptoms. 
1429 
do 
6 
do 
No symptoms. 
1427 
. ..do 
7 
do 
No symptoms. 
1430 
do 
7 
do 
Slight symptoms. 
1431 
do 
8 
do 
Slight symptoms. 
1432 
do 
8 
do 
Slight symptoms. 
1433 
do 
9 
do 
Slight symptoms. 
1434 
. ..do 
9 
do 
Slight symptoms. 
1435 
. . o 
10 
do 
Marked symptoms. 
It will be seen from the above work that the period of incubation is 
about seven days or less in guinea pigs sensitized in the brain and about 
nine days in guinea pigs sensitized subcutaneously. So far as may 
be judged, it therefore appears that the period of incubation is some- 
what shorter in guinea pigs sensitized in the brain than those sen- 
sitized subcutaneously. It also seems quite evident that the sen- 
sitization comes on somewhat gradually. Judged by our own results 
and the work of others, the period of incubation is quite constant. 
Lewis® states that the incubation period is not to be considered 
as abruptly terminating at a given day. He says that he has made 
an animal quite sick by the intracardial injection of 2 c. c. of serum 
on the sixth day after a toxine-antitoxin mixture. 
« Lewis, Paul A. ; The induced susceptibility of the guinea pig to the toxic action 
of the blood serum of the horse. Journ. Exper. Med., vol. 10, No. 1 , Jan. 1, 1908, p. 1. 
