94 
may produce a hypersusceptibility and also a certain degree of 
immunity. Now that we have proved that this hypersusceptibility 
or anaphylactic action in the case of horse serum may be transmitted 
hereditarily in guinea pigs, may it not throw light upon the fact that 
tuberculosis “runs in families?” 
Demonstrations of the hereditary transmission of acquired charac- 
ters are comparatively rare in biology. While there are several 
recorded instances demonstrating that immunity to certain infectious 
diseases may be transmitted from a mother to her } r oung, yet, as far 
as we know, this is the first recorded instance in which hypersensi- 
tiveness, or anaphylaxis, has been experimentally shown to be trans- 
mitted from a mother to her }mung. 
Other albuminous substances, such as skimmed milk, peptone, 
hemoglobin, egg albumin, and vegetable prot.eids possess no poison- 
ous action upon guinea pigs sensitized with horse serum. Whether 
guinea pigs are rendered susceptible to a subsequent injection with 
the same albuminous matter with which they have been sensitized 
will be reported in a later paper. 
We believe that the substance which sensitizes the animal is iden- 
tical with that which later poisons it. However, the substance must 
first cause a reaction in the organism resulting in a production of 
antibodies. We have found that small quantities of horse serum pro- 
duce, after a definite period of incubation, a condition of anaphylaxis; 
multiple or repeated injections produce immunity. We therefore 
possess in horse serum a substance capable of causing both anaphy- 
laxis and prophylaxis. 
It may be that man can not be sensitized in the same way that we 
have shown to be the case with guinea pigs. Children have, in a num- 
ber of instances, been injected with antidiphtheric horse serum at 
short and long intervals without, so far as we are aware, causing 
death. Certain serums, for example, the antitubercle serum of 
Maragliano and the antirheumatic serum of Menzer, are habitually 
used by giving injections at intervals of days or weeks. In all such 
cases of frequent and repeated injections the amount which has been 
injected and the interval between the injections must be taken into 
account in relation to our work. Yon Pirquet and Schick have shown 
that a second injection of horse serum into children causes an “imme- 
diate” or an “accelerated” reaction. Both the immediate and the 
accelerated reaction in children are characterized by symptoms of 
“the serum disease.” 
We might conclude that children may not be sensitized to the toxic 
action of horse serum by eating horse meat, for horse meat is a favorite 
article of diet in certain European countries and there is nothing upon 
record to show that the injection of horse serum in those countries is 
fraught with more danger than where this diet is not used. It should, 
