1889.] Etiological Classification of Diseases. 965 
the other faculative, or acquired by the individual. Or, in other 
words, the one form cannot be presented by the individual, hence 
is obligatory, while in the other he acquires the " faculty " of in- 
toxicating himself 
To return to invasive complications : Correctly speaking, 
every lesion of parasitic origin must be considered as invasive in 
which specific pollution of the blood is not directly produced by 
the invader. 
It has been said, and must be repeated, that the experimental 
test of this point must be made on healthy individuals of the same 
species in which the parasite was discovered, and if a micro- 
organism, by sub-cutaneous injection only. 
I insist on the latter point with as much intensity as on the 
others that have been raised. 
For instance, there are many micro-organisms found in the 
respiratory tract of animal life, or in the intestines, some of which 
under circumstances cause local lesions, and yet not one of them 
need necessarily be specifically infectious in or to the species of 
animal in which it was discovered. On the other hand, they 
may be violently so — septicaemic in rabbi ts, mice, guinea-pigs, or 
some of the many animals used in experimentation, the cele- 
brated sputum coccus for example, and the majority of such 
organisms lately described by Miller in his work on " Bacteria in 
the Mouth." There are quite a number of such in the intestinal 
canal of hogs, but of those which I have thus far tested on rab- 
bits, guinea-pigs, mice and ground-squirrels, and found fatal to 
one or the other, not one affected pigs in the least in very large 
amounts when introduced in the same way; that is, sub-cutane- 
ously. 
This class of germs is not specific in any sense of the word, 
according to our present knowledge. Not one of them is known 
to be the cause of a natural infectious disease in any of the animals 
in which they have been shown to have septic action by experi- 
mental inoculation. They should not even be called " pathogenic," 
as has been the case, as the word is misleading, and has too much 
of a specific sense to be used in this connection.* 
