38 
Transactions Texas Academy of Science.— 1907. 
the phagocytes of the blood will take in is a matter of immunity the 
animal has acquired against this species of bacteria— -the phagocytes of 
an immune person will take in a great number of the bacteria, while 
the phagocytes of a non-immune person will take in very few or no 
bacteria. 
There is another important and suggestive phase to this subject, the 
explanation of which seems to afford strong evidence in favor of the 
biophysical theory. It is this, inoculations, whether made of bacteria, 
toxins, ferments, or proteids, do not cause a development of antibodies 
(immune bodies), or, if you please, opsonins in the serum and tissue 
juices of immune persons; these develop only when inoculations are 
made in person who are non-immune to the substances inoculated. 
These facts do not seem susceptible to explanation except upon the 
hypothesis that the reactions which occur in these processes are those 
of ferments on vulnerable substrates, and since such substrates are either 
destroyed or thrown out of commission through a loss of vulnerability 
by the action of the bacteria, ferments, toxins, or proteids, in the ac- 
quirement of immunit}^, a development of antibodies can not follow 
inoculations while the immunity of the animal organisms continues to 
exist. There is still another phase to this subject, and a very remark- 
able one, that has only recently received much notice. I refer to the 
deadly effect that an infinitesimal dose — 1-10 c.c. — of horse serum (a 
harmless substance) will produce when inoculated into a guinea pig 
which has been made sensitive to horse serum by a previous inocula- 
tion of 1-250 or even 1-10,000 c.c. of serum when the interval of time 
between the doses was as much as ten days. 
Horse serum is practically innocuous to the guinea pig and to other 
animals when given in a single dose, or in repeated doses when given 
at short intervals; in fact, the latter method will immunize the animal. 
But when an interval of ten days to as many months is permitted to 
elapse between the inoculations the second dose will kill the pig in a 
brief time, even though the dose does not exceed 1-10 c.c. This extra- 
ordinary phenomenon appears susceptible to but one interpretation, that 
of ferment action. It is fortunate that horse serum does not react with 
the serum of man as it does with the serum of the guinea pig; if it did 
the world would be deprived of the benefits of one of its most beneficent 
discoveries — the antitoxin treatment of diphtheria. 
A suggestive feature of the toxicating of horse serum for the guinea 
pig by* the administration of small, sensitizing doses of serum is the 
specificity of the reaction. Horse serum in quantity as small as 1-250 
c.c. can alone sensitize a guinea pig to the extent that it will be killed 
by a second dose of the serum, — even the 1-10 c.c. when given after the 
period of incubation has passed. It is claimed that guinea pigs have 
