276 PROTECTIVE INOCULATIONS. 



tious material introduced had previously been insisted upon by Da- 

 vaine in his paper entitled " Eeclierclies sur quelques lines des conditions 

 qui favorisent ou qui empechent le development de la septicemie," pub- 

 lished in the Bulletin of the Academy of Medicine, seance of February 

 18th, 1879. 



Davaine says : 



"A third condition relates to the quantity of bacteria introduced into the 

 tissues. This question of quantity has been made manifest in our experi- 

 ments. Not only does it differ in different species of animals, the rabbit and 

 the dog, for example, but it varies in different animals of the same species." 



In his communication to the Academy of Sciences, made on April 

 4th, 1881, Chauveau gives the results of his experiments in producing 

 immunity by inoculations with very small quantities of virus. After 

 some preliminary experiments with a larger number, five sheep were 

 inoculated with diluted anthrax blood estimated to contain two hun- 

 dred and fifty bacilli for each. All of the animals survived the inocu- 

 lation after having manifested some slight febrile reaction. Six weeks 

 later all were reinoculated with a dose which should have been fatal 

 to an unprotected animal. One of the animals died of anthrax, the 

 other four resisted perfectly. 



On June 26th, 1882, Chauveau reported to the Academy of Sciences 

 the results of his experiments relating to the protection of animals 

 from anthrax infection by the method of Toussaint. By carefully 

 conducted experiments Chauveau found that nine or ten minutes' ex- 

 posure to a temperature of 54 C. killed all of the bacilli in anthrax 

 blood, and the same result was obtained by sixteen minutes' exposure 

 to 52 C., while at 50 C. the time required is twenty minutes. An 

 attenuated virus suitable for protective inoculations is obtained by 

 exposure for a somewhat shorter time, and as a result of his experi- 

 ments Chauveau was led to the conclusion that for a first inoculation 

 anthrax blood heated to 50 C. for fifteen minutes afforded a good at- 

 tenuated virus. This was to be followed after an interval of ten to 

 fifteen days by a second inoculation with a stronger virus, obtained 

 by exposing anthrax blood to the same temperature (50 C.) for nine 

 or ten minutes. These inoculations sufficed to protect the animals 

 when they were subsequently inoculated with virus of full strength 

 blood from an animal which had recently succumbed to the disease. 

 Chauveau says with reference to this method : 



" In one hour, with a single guinea-pig [dead of anthrax], it is easy to 

 prepare the quantity of vaccine required to inoculate more than five hundred 

 sheep. The inoculation is made with the point of a lancet, charged, by the 

 method in use in my laboratory, with a very small quantity of virus. Two 



