PROTECTIVE INOCULATIONS. 



the dura mater, with greater certainty than by subcutaneous inocula- 

 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 (18S5) claims to have demonstrated the presence of minute 

 cocci, 0.2 fj. in diameter, in sections of spinal cord from rabid ani- 

 mals, by Weigert's method of staining. The cords were hardened in 



