418 RABIES 



of glycocholate of soda. A mixture of this with an equal amount 

 of serum is incubated for five hours, and observed after it has 

 stood sixteen to twenty hours at the room temperature. The 

 precipitate is specially obvious near the surface. 



Fornet, Schereschewsky, Eisenzimmer, and Rosenfeld find 

 that the sera of syphilitics in the early stages of the disease 

 contain a precipitogen which forms an insoluble compound with 

 a substance or precipitin present in the serum of tabetics or 

 general paralytics. When the one is floated on the other, a 

 characteristic ring appears at the area of contact. They say that 

 normal serum rarely contains the precipitin, but not the 

 precipitogen. What relation this has to any immunity reaction 

 is unknown. 



Rabies. 



The actual causal agent of rabies is not yet definitely ascertained. 

 The peculiar structures known as the corpuscles of Negri which 

 occur in the brain, and especially in the hippocampus major, of 

 rabid animals appear to be quite characteristic of the condition, 

 and may possibly be the actual parasite, although this is not yet 

 universally accepted. It seems, however, fairly certain that their 

 recognition constitutes a sufficient proof of the presence of the 

 disease ; and this is of great importance in view of the necessity 

 for the early commencement of the treatment, which is entirely 

 preventive, and not curative. If the dog by which the patient has 

 been bitten is forthcoming, the corpuscles of Negri can be demon- 

 strated in a short time by simple methods, and the need for 

 Pasteur's treatment ascertained ; apart from this the only method 

 is by animal inoculation, an emulsion of brain substance being 

 injected into the brains of rabbits after trephining. 



Rabies presents one of the most striking examples of local 

 immunity ; the action of the virus is manifested almost entirely 

 on the central nervous system, and in whatever part of the body 

 the inoculation is made the effects are only caused when it has 

 reached the brain and spinal cord ; and in doing so it does not 

 gain access to the blood, but ascends the peripheral nerves. 

 Hence the central nervous system is extremely susceptible to 

 injection, and the other tissues in proportion to their richness in 

 nerves. Subcutaneous (unless into a region like the paw), intra- 

 venous, or intraperitoneal injections only convey the disease if a 

 large amount of extremely potent virus is used. Hence it seems 



