PROTECTIVE INOCULATIONS. 827 
the dura mater, with greater certainty than by subcutaneous fnocula- 
tions. But the exact nature of this virus has not been determined. 
The fact that a considerable interval elapses after inoculation before 
the first symptoms are developed indicates that there is a multiplica- 
tion of the virus in the body of the infected animal; and this is further 
shown by the fact that after death the entire brain and spinal marrow 
of the animal have a virulence equal to that of the material with which 
it was inoculated in the first instance. The writer’s experiments 
(1887) show that this virulence is neutralized by a temperature of 60° 
C., maintained for ten minutes—a temperature which is fatal to all 
known pathogenic bacteria in the absence of spores. But recent ex- 
periments show that certain toxic products of bacterial growth are 
destroyed by the same temperature. We are, therefore, not justified 
in assuming that the morbid phenomena are directly due to the pres- 
ence of a living micro-organism; and, indeed, it seems probable, from 
what we already know, that the symptoms developed and the death of 
the animal are due to the action of a potent chemical poison of the 
class known as toxalbumins. But, if this is true, we have still to ac- 
count for the production of the toxic albuminoid substance, and, in 
the present state of knowledge, have no other way to explain its in- 
crease in the body of the infected animal than the supposition that a 
specific, living germ is present in the virulent material, the introduc- 
tion of which into the body of a susceptible animal gives rise to the 
morbid phenomena characterizing an attack of rabies. 
Pasteur and his associates have thus far failed to demonstrate the 
presence of microorganisms in the virulent tissues of animals which 
have succumbed to an attack of rabies. Babes has obtained micro- 
cocci in cultures from the brain and spinal cord of rabid animals, and 
states in his article on hydrophobia in “ Les Bacteries”” (second edi- 
tion, p. 791) that pure cultures of the second and third generation in- 
duced rabies in susceptible animals; but his own later researches do 
not appear to have established the etiological relation of this micro- 
coccus. 
Gibier (1884) has reported the presence of spherical refractive 
granules, resembling micrococci, in the brain of rabid animals, which 
he demonstrated by rubbing up a little.of the cerebral substance with 
distilled water. As these supposed micrococci did not stain with 
the usual aniline colors and were not cultivated, it appears very doubt- 
ful whether the refractive granules seen were really microorganisms. 
Fol (1835) claims to have demonstrated the presence of minute 
cocci, 0.2 » in diameter, in sections of spinal cord from rabid ani- 
mals, by Weigert’s method of staining. The cords were hardened in 
