Part IX* 
MATERNAL' TRANSMISSION OF HYPERSUSCEPTIBILITY AND ' 
IMMUNITY. 
In our previous work we showed that hypersusceptibility to the 
toxic effects of horse serum ma}" be transmitted from the mother 
guinea pig to her young. Later, one of us (Anderson) showed that 
the female guinea pig ma}^ transmit hypersusceptibility to horse serum 
and immunity to diphtheria toxine at the same time. On account of 
certain analogies between the reaction to tuberculin and the toxic 
action of horse serum, we have made further studies along these lines. 
In this bulletin we shall refer only to our studies upon the transmis- 
sion of hypersusceptibility and immunity to the toxic action of horse 
serum, leaving related studies with' tuberculosis and tuberculin for a 
future publication. 
Our present studies corroborate the fact that hypersusceptibilit}- to 
the toxic action of horse serum is alwavs transmitted from the mother 
guinea pig to her }’oung. This function is solely maternal; the male 
takes no part whatever in the transmission of these acquired proper- 
ties. Whether this maternal transmission is hereditary or congenital 
can not be definitely stated. 
We are able to exclude the milk as a factor in transmitting the 
hypersusceptibility to the toxic action of horse serum by a series of 
exchange experiments, which are given in detail below. 
“Exchange” experiments consist in at once placing guinea pigs 
born of a susceptible mother to nurse with an untreated female and, 
in exchange, the }mung of the untreated female are at the same time 
placed to nurse with the susceptible female. From these “exchange” 
experiments we learn that the hypersusceptibility is not transmitted 
to the }mung in the milk. 
We also learn from our experiments that hyper susceptibility may 
be transmitted from mother to t'oung whether the mother is sensitized 
before or after conception. The fact that this influence may take 
place after conception might be taken to indicate that the transmission 
is congenital and not hereditary. 
GROUP A. 
FAMILY NO. I. 
(Sensitized female; untreated male. ) 
Female (G. P. No. 610). October 20, 1906. Six c. c. antitoxic horse serum. (Natl. 
IX, 17) intraperitoneally. Dead, 30 minutes. 
[Previous treatment: 151 days prior, 0.15 c. c. toxine No. antitoxic 
horse serum (Natl. YIII, 18).] 
( 47 ) 
