48 
marrow a few centimetres in length in dry air, the degree 
of attenuation being directly proportionate to the time of 
exposure, the dimensions of the fragment, and the tempera- 
ture ; the rabid property of the marrow being ultimately 
extinguished. The lower the temperature the more slow 
is the process of attenuation. By this process a graduated 
series of infective material, suitable for prophylactic inocu- 
lations, is obtained. M. Pasteur then says : If the rabid 
marrow be kept from contact with the air, in carbonic acid 
gas, in a moist state, the virulence is maintained undimi- 
nished (at least for several months), provided that it is pro- 
tected from foreign microbic alteration.” 
M. Pasteur has not yet discovered any microbe as peculiar 
to rabies, though the fact that a perfectly definite period is 
required for the development of the disease when the virus 
is introduced directly to the nerve centres, which appear to 
constitute its appropriate nidus, is suggestive of the exis- 
tence or evolution of a specific microbe. It is also as yet 
a mystery as to how, in the case of an ordinary bite, the 
affection is conveyed to the nerve centres, whether, by trans- 
mission through the blood, the specific infection ultimately 
obtains a lodgment in the ganglia suitable for its incubation, 
or whether an influence is conveyed through the nerves 
which sets up corresponding changes in Bechamp’s hypothe- 
tical micro-zymes in the nerve centres, thus evolving from 
healthy material morbid organisms whose action is identical 
with that of the disturbing causes. 
In this latter supposition we seem to see something 
analogous to induced electricity, and I may add that, through- 
out the whole of the phenomena of zymotic disease, there is 
a suggestion of action with corresponding and intensifying 
re-action. Given a micro-organism producing a certain 
effect upon an environment, that effect, in the absence of 
disturbing influences, seems to re-act upon the organism 
itself and increase its ability to re-produce the specific effect. 
