TEXAS FEVER. 
97 
tetanus, led to the somewhat broad statement by Behring, one of 
the chief investigators of serum therapy, “that if an animal has 
acquired immunity against a disease-producing micro-organism, 
or its toxins, the serum from the blood of the immunized ani¬ 
mal will prevent the disease in another susceptible animal.” 
While Texas fever is due to a protozoan micro-parasite 
instead of bacteria, as in the case of diphtheria, the immunity 
attained on recovery from an attack of the disease appears to be 
as great as in the latter malady. And it was not unreasonable 
to suppose that, in the physiological processes by means of 
which immunity is established against Texas fever, some new 
product should be formed which might stimulate in the cells of 
a susceptible animal, a condition of metabolism like that of the 
cells of the immune animal, and thus establish at least a pas¬ 
sive immunity that would tide the animal over the danger- 
period following tick-infestation. 
The first experiment with sterile serum inoculation was 
made in the fall of 1896, on an eight-year-old cow. 200 c.c. of 
serum were inoculated subcutaneously during a couple of weeks 
previous to infesting her with ticks. After the infestation, this 
cow was inoculated with 80 c.c. more of serum. This inocula¬ 
tion began September 2d ; the infestation was. made Septem¬ 
ber 16th, and the animal was kept under observation until No¬ 
vember 2d, morning and evening temperatures being taken. 
During this time there was no elevation of temperature, except 
on the afternoon of 17th and 18th days following tick-infesta¬ 
tion, 103.8 E. and 106 F. Outwardly, the animal appeared to 
be in perfect health throughout the experiment. 
The following spring, in conjunction with the Mississippi 
Experiment Station, a lot of young cattle and one cow were 
inoculated at Enterprise, Mississippi. These had all sickened 
from accidental tick-infestation. Twelve other cattle had died, 
all but two of them being adult animals. All the inoculated 
animals lived. A full report appears in Bulletin No. 37, of the 
Missouri Experiment Station, where the method of preparing 
the serum is described. 
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