95 
however, be borne in mind that our work has shown that guinea pigs 
may be sensitized with exceedingly minute quantities of a strange 
proteid, and that repeated injections cause an immunity, and it does 
not seem impossible that the same action may be true of food. 
Man reacts to the first injection of horse serum after a period of 
eight to thirteen days; guinea pigs show no reaction as a result of the 
first injection; both man and guinea pigs react to a second injection. 
The reactions in man and the guinea pig differ, however, both in sever- 
ity and in kind. The relation, therefore, that our observations upon 
the guinea pig may have in their application to man must await fur- 
ther study. 
The fact that other animals beside man ana the guinea pig react to 
a second injection of horse serum would seem to indicate that we are 
dealing with one and the same action. 
We believe that our results make it probable that man may be ren- 
dered sensitive to the injection of a strange proteid, as is the case with 
the guinea pig and other animals, and that this explanation must be 
considered as well as the status lymphaticus, which has heretofore been 
assigned as the cause of sudden death following the injection of horse 
serum. 
[Post Scriptum. — After the galley proof of this article had left our 
hands an article by R. Otto entitled “ Das Theobald Smithsche Pha- 
nomen der Serum-Ueberempfmdhchkeit," reprinted from Leuthold- 
Gedenkschrift, band 1, first came to our notice. His paper deals 
with some of the problems we have studied and his results are in 
harmony with many of our conclusions.] 
O 
