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oratory animals, caused severe symptoms and in one instance when 
fed to a puppy produced fatal diarrhea. 
Following Fliigge, attention was focused upon the peptonizing 
action of bacteria. The evidence is contradictory, but for the most 
part, Fliigge’s contentions have not been confirmed. Recent investi- 
gations show that the cleavage of proteids by bacteria is much more 
like that caused by the digestive juices than has heretofore been sup- 
posed. There is little evidence for the view that poisonous substances 
can be formed by the direct cleavage of proteids by bacteria ; in fact 
the two best known of the bacterial poisons (diphtheria and tetanus 
toxines) can be produced in proteid-free media. 
The bacterial toxines . — Much has been written upon “ toxines ” in 
milk. However, when we sift the matter down we find that we 
know practically nothing of the true bacterial toxines concerned. 
Toxines are soluable chemical substances of unknown composition 
that produce poisonous symptoms after a definite period of incuba- 
tion and are capable of inducing immunity as a result of the produc- 
tion of antibodies. 
We are acquainted with very few bacterial toxines. The best 
examples are tetanus, diphtheria, and the toxine produced by the 
Bacillus botulismus. These toxines are not resistant to heat; they 
are all rendered practically inert at a temperature of 60° C. 
Bacterial toxines are not the result of proteolytic action upon the 
albumins contained in the media in which they grow. They may 
be secreted by, or result from, the breaking down of proteids of the 
bacterial cell. Concerning their mode of production and their chem- 
ical nature we have no definite knowledge. 
None of the true toxines are poisonous when taken by the mouth 
except the botulism toxine. For instance, the strongest one known 
(tetanus) is harmless when taken by the mouth.® We have given a 
guinea pig 24,000 and a mouse 8,000 minimal lethal doses by the 
mouth without appreciable effect. It is, therefore, plain that the 
effects of a toxic substance found in milk when injected into labora- 
tory animals is no criterion of its effect when taken by the mouth. 
Particular attention is drawn to this fact because much of the 
experimental work upon the poisonous substances in milk has been 
done by injecting these substances into the tissues of lower animals. 
It is now plain that violent poisons, when introduced subcutaneously, 
may be inert when taken by the mouth. We must also be cautious 
in interpreting feeding experiments upon lower animals as applied 
to man, especially when we consider the great differences in sus- 
ceptibility of the gastro-intestinal tracts of different species. This 
difference is marked even among infants, for there is evidence in 
° Snake vemon is also harmless by the mouth. 
