616 RABIES AND THE NEGRI BODIES 



way to the injection of the fixed virus, is shown by the fact that they 

 have occurred in persons who, as shown subsequently, were not 

 bitten by rabid dogs, but who received the Pasteur treatment. Almost 

 all of these cases end in complete recovery. There is, however, one 

 case reported, that of a man sixty-two years old, who died, but it is 

 doubtful whether he died in consequence of the Pasteur treatment 

 or from some other cause. 



Differences in Virulency between Street and Fixed Viruses. The 

 fixed virus, while of a maximum virulency subdurally for rabbits 

 and other animals, if injected by any other route, exhibits a de- 

 creased virulency and can be used for immunizing purposes. Marx, 

 discussing the differences between street and fixed virus, comes 

 to the following conclusions: The fixed virus produces a more 

 abundant or a more powerful toxin than the street virus. The rate 

 of velocity of multiplication of the fixed virus is greater than that 

 of the street virus; the fixed virus in purely subcutaneous inoculation 

 is absolutely harmless for man and apparently much less virulent for 

 animals than the street virus. For some animals it is also less virulent 

 in intramuscular (monkey) and in intraocular (monkey, rabbit) inoc- 

 ulation. This behavior can only be explained everything being 

 equal by assuming that the fixed virus is more easily destroyed by 

 the protective powers of the body than the street virus. 



The question then naturally arises, Why should the stronger, more 

 rapidly multiplying, fixed virus be more easily destroyed by the 

 protective powers of the body? Marx and others, discussing this 

 point, do not offer any explanation. The following, however, suggests 

 itself to the author: 



In natural infection the virus, in order to produce rabies, must be 

 able to wander in some way from the portal of entrance, mainly 

 along the peripheral nerves to the central nervous system, there to 

 invade the ganglion cells, to multiply and to produce the specific 

 disease hydrophobia. By injecting the street virus for a number of 

 generations subdurally, a method of procedure which, of course, is 

 highly unnatural, we artificially breed an abnormal race of micro- 

 organisms. These become more highly specialized in their parasit- 

 ism and lose their organs of locomotion or other apparatus, which 

 enabled them to travel from a portal of entrance in the subcutaneous 

 connective tissue to the central nervous system. The statement 

 about the loss of organs of locomotion is, of course, not to be taken 

 literally, but simply in the same sense as Ehrlich has depicted as 

 definite geometrical bodies, antigens and antibodies, amboceptors, 

 complements, etc., in order to give a clear idea of their combination 

 neutralization, fixation, lysis, agglutination, etc. 



If the microorganisms of rabies in consequence of continued sub- 

 dural injection have lost the power to travel from any outside place 

 toward the central nervous system, they will be destroyed in loco 

 by the protective powers of the invaded organism, and while this 



