FOWL CHOLERA. 
341 
determining the active principle of even this cultivated vims: 1. 
The pathogenic agent may be a soluble ferment. 2. It may be 
living particles (bioplasm) extremely minute, or having the same 
refractive index as the liquid in which it multiplies, and therefore 
invisible. 3. It may be the bacteria to which our attention has 
already been directed. Pasteur has shown that by filtering the 
cultivated virus through plaster, the solid particles are removed 
and the limpid liquid which is obtained is perfectly harmless, 
even when injected under the skin of susceptible birds in consid¬ 
erable quantities. Objection being made to the filtering as liable 
to remove some dissolved bodies as well as the solid particles, 
the same able investigator has given us another and very valuable 
demonstration. If tubes containing cultivated virus are placed 
where the temperature is constant, the micrococci are all deposit¬ 
ed on the bottom of the apparatus, leaving a perfectly limpid 
liquid above them. Inoculations with this liquid prove it to be 
as harmless as that which has been filtered.* 
Even this demonstration was insufficient to convince those who 
oppose the germ-theory—the ferment might be very volatile and 
escape from the upper layers of the cultivation-liquid, or it is at¬ 
tached to the bacteria themselves, and can only be introduced 
with them. To meet such objections the writer has carried 
through an entirely different line of investigation. It was found, 
after considerable experimenting, that the activity of the virus is 
destroyed at a temperature of 132 deg. Fahr., if maintained for 
fifteen minutes—a temperature so low that few, if any chemical 
bodies would be affected by it if protected from atmospheric 
gases and evaporation. Small glass tubes were, therefore, com¬ 
pletely filled with virus, hermetically sealed, and placed for a 
quarter of an hour in water of this temperature. Here there was 
no chance for any constituent to escape, and the dead organisms 
might be introduced into the inoculation-punctures with whatever 
chemical products there might be adhering to them. Now, what 
is the result of inoculations with virus treated in this way ? Ex¬ 
perience shows that a million times as much as produced death 
* Bulletin de VAcademie de Medecine, 1880, p. 530, 
