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592 
more labor than the other, but the mortality is less and more reactions 
are obtained than by any other. 
It is necessary to standardize any serum for the race of cattle on whiclr 
it is to be used for the purposes of inoculation and to this end a number 
of cattle should be inoculated each with 1 cubic centimeter of virulent 
blood and with 10, 20, 30, and 40 cubic centimeters of serum. ‘The 
efficient dose is the one which allows a febrile reaction to take place but 
after the administration of which the animal shows no other symptom 
of the disease. In certain cases 20 cubie centimeters will accomplish 
this result, at least this is as a rule the minimal efficient dose of serum 
for the race of cattle with which we have to deal in the Philippine 
Islands; however, even here it will be found that this amount will vary 
with the racial susceptibility and in a number of instances must be much 
increased. 
Passive immunity by the use of serum.—The method for obtaining 
passive immunization has been indicated in the section on preparation 
of serum; its origin lay in the observation that the serum obtained from 
naturally salted cattle possessed a slight immunizing power and that by 
the use of large doses, a temporary immunity could be established 
which would protect otherwise non-immune animals against the natural 
or inoculated disease. 
Several workers, in continuing the study of the natural process, by injecting 
successively increasing amounts of virulent blood into salted animals, were able 
to produce a very efficient serum which could be used successfully in doses of 10 
to 20 cubie centimeters (Kolle and Turner). Such a serum is also stated to 
possess curative power. 
The immunity resulting by the use of serum alone is transient ; accord- 
ing to various observers it varies from several weeks to a number of 
months, depending upon the quantity employed which has been injected 
into the animal; 100 to 200 cubic centimeters may produce an immunity 
which will last through the more extended period. 
The advantages of the serum method are that there Is no reaction, 
that no unfortunate results follow in dairy or pregnant cattle, that it 
‘In our work repeated injections of large amounts of antirinderpestic serum 
in certain races of cattle before active immunization with virulent blood and 
serum have not given favorable results. These repeated large doses of serum 
were employed in a number of American cattle in which it was considered advisable 
to produce a passive immunity at a time when, owing to a long voyage or for 
other reasons, they were not considered in a sufficiently good general physical 
condition for active immunization. Many of these animals (which were inoculated 
with repeated does of serum) and with virulent blood some days after the injec- 
tion of the first large dose of serum, succumbed to a severe infection of rinderpest 
or of rinderpest in combination with Texas fever. 
Apparently, the repeated doses of serum produced antibodies in the animal 
body.—P. C. F. 
