STREPTOCOCCI IN COMPARATIVE PATHOLOGY. 
853 
causal relation to the disease or be accounted for by their rapid 
proliferation in native soil made favorable for their excessive 
increase by the conditions produced by the true etiological fac¬ 
tors. Their natural distribution is so wide, and their virulence 
so capricious that a secondary invasion, which seems always to 
be possible, renders the fixing of etiological responsibility upon 
■ a streptococcus isolated from any diseased tissue a somewhat 
difficult task. The problems in this connection which concern 
us most and which need more extended investigation pertain 
(i) to the determination of the parasitic possibilities of strepto¬ 
cocci existing in nature, i. e., those ordinarily considered as sap¬ 
rophytes and, (2) to the distinction, if it exists, between strep¬ 
tococci which are able to produce local inflammatory processes 
leading to suppuration and those which produce highly infect¬ 
ive and rapidly spreading diseases, such as erysipelas and pos¬ 
sibly strangles and Brustseuche. 
ANTISTREPTOCOCCIC SERUM. 
The questions which are asked most frequently concerning 
the practical side of this subject pertain to the antitoxin or an¬ 
tistreptococcic serum. Certain temptations have been placed 
before the veterinary practitioner by way of attractive and 
assuring advertisements of such products. The beneficent re¬ 
sults from diphtheria antitoxin seem to attract people toward 
serum therapy with more hope than knowledge concerning the 
properties or probable therapeutic action of the serum to be 
used. It is not pleasant to put even the proverbial straw in 
the way of the enthusiasm over serum therapy, but in a sober 
consideration of the practicability of the widespread use of an¬ 
tistreptococcic serums in the diseases heretofore mentioned in 
which streptococci are associated and where they stand in a 
possible causal relation to the disease, certain important facts 
must be taken into account. 
If I have succeeded in conveying the facts as I see them 
concerning the relation of streptococci to animal diseases, it is 
clear that there is a large number of these organisms which 
are likely to invade the animal body either as primary factors 
