The Keys of Death : 
211 
1879:. 
known — which, when absorbed by an animal, bring on such 
diseases as rabies, small-pox, cholera, dysentery, typhoid, 
and the whole class of so-called zymotic affections. On the 
other hand, there are the true poisons, such as arsenic, 
strychnin, aconitin, hydrocyanic acid, &c. The substances 
of this latter class are well-defined chemical individuals, 
and even when, as is the case with all the most deadly, 
they are of vegetable or animal origin, — an awkward faCt 
for the charlatans who guarantee the “ purely vegetable ” 
nature of their life-pills, — their efficacy has no connection 
with vitality. Poisons of this class when introduced into 
the system set up morbid aCtion almost immediately, and if 
the dose be sufficient, and if no remedial measures are 
adopted, the symptoms go on increasing in violence without 
intermission until death ensues. A characteristic feature is 
that their noxious power may be decreased, or even totally 
extinguished, by dilution. If a pound of arsenic, or even 
of aconitin, were dissolved in the head-waters of! the 
Thames, not the least danger would result to any of the 
thousands of people who drink Thames water as supplied 
to certain districts of London. The ferments, on the con- 
trary, are not definite chemical principles, capable of being 
isolated, of entering into combination with other bodies, and 
of being separated again. So far as we know they are living 
organisms of low type, belonging to that “ debatable land ” 
that lies on the margins of the animal and the vegetable 
kingdoms, and they retain their virtues, or vices, only so 
long as their vitality endures. If swallowed, or otherwise 
introduced into the system, no evil effeCt is perceived for 
some time. There is a so-called “ period of incubation ” 
which in the case of rabies may extend over months, or even 
years, before the symptoms of disease make their appear- 
ance. Another characteristic is that the poison is multiplied 
in aCting. If we kill an animal by the administration of a 
dose of strychnin or of arsenic, we cannot obtain from its 
body any more poisonous matter than we put in ; but if we 
inoculate an animal with a ferment-poison we find in some 
cases its blood, in others its secretions and excretions, 
capable of reproducing the same disease in other animals. 
The ferment grows and fructifies in its victim, just as does 
wheat in a field. The ferments, too, lose none of their 
deadly power by dilution. If, returning to our former ex- 
ample, we placed a quantity of the excretions of a cholera 
patient or of a victim of typhoid fever in the head-waters 
of the Thames, there would be great danger to persons sup- 
