462 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1915. 



Since antianthrax vaccinations are a protection against possible 

 contamination, it will be asked if a similar method would not be 

 effective during incubation — that is, between the time when the 

 virus is introduced into the organism and the time when the symp- 

 toms appear. It was also Pasteur who brought up and solved this 

 problem. 



It was already known that it was possible to confer immunity 

 against rabies. A professor at the veterinary school of Lyon, Gal- 

 tier, had shown that the saliva of a mad dog injected in the veins 

 of a sheep or goat did not provoke symptoms, but conferred a power- 

 ful resistance against a later inoculation of the virus. The discovery 

 was important but was devoid of practical interest, as the method 

 was uncertain and dangerous. 



Taking up the study of this question, Pasteur, in collaboration 

 with Chamberland, Roux, and Thuillier, recognized that inoculations 

 performed under the cerebral duramater with the emulsion of a 

 fragment of bulb taken from a dog which had died from rabies were 

 certain to transmit the disease. Using a rabbit, if the inoculations 

 are made in series, the virulence increases — that is, the time of incu- 

 bation diminishes: it becomes only 6 or 7 days after a hundred 

 passages, and from this time it no longer varies; from then on the 

 virus is fixed. 



If the spinal marrow of a rabbit which has succumbed to an inocu- 

 lation of the fixed virus is suspended in a sterilized flask containing 

 a substance free from water, such as fragments of potassium, it was 

 learned that under the influence of drying the virulence diminishes, 

 and at the end of 14 days the organism becomes accustomed to 

 supporting viruses more and more active. As the incubation of the 

 disease — that is, the time which elapses between the bite and the 

 first symptoms — ^lasts a very long time, and as the process of render- 

 ing immune is relatively rapid, the refractor}^ state is successfully 

 reached before the appearance of symptoms. 



The treatment varies according to the location, the extent, the 

 depth, and the number of bites. It lasts from 15 to 22 days and 

 consists essentially in injecting at different intervals fragments of 

 marrow, beginning with those dried for 14 days and gradually 

 progressing to those dried only 3 days. 



It is useless to dwell on the results obtained. Pasteur's method 

 is causing the gradual disappearance of rabies, and the time can 

 be predicted when this terrible infection will join smallpox and 

 anthrax in the group of historic diseases. 



Against smallpox, anthrax, and rabies immunity is secured by 

 means of living virus. It is Imown to-day that all the effects pro- 

 duced by microbes are due to substances which they contain or 

 which they secrete. Experience shows that it is possible to obtain 



