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dogs in keeping up a constant supply of vaccine, which is 

 easily done by killing one rabbit every week by inoculating 

 it with virus of maximum strength. The rabbit so inoculated 

 on Saturday dies in Pasteur's laboratory on the following 

 Friday, and on the next day (Saturday) another rabbit is 

 inoculated with the virus taken from the dead rabbit. This 

 also, in its turn, dies on the following Friday, and a third 

 rabbit is inoculated on the third Saturday, and so on per- 

 petually. The standard virulent virus so obtained every 

 Saturday is employed in preparing the vaccine. 



1,333. The dead rabbit is dissected, its spinal marrow 

 taken out, and hung inside a glass jar containing potash at 

 the bottom, the jar being placed in a room regulated at a 

 constant temperature of 20 C. The spinal cord thus gets 

 drier and drier, the potash preventing putrefaction, and in 

 drying up it gets more and more attenuated. But even after 

 seven days of desiccation it is capable of killing rabbits. On 

 the 8th day it is harmless for rabbits, and probably much 

 more so for men. But to be more careful the first vaccina- 

 tion applied to man is made with the spinal cord desiccated 

 for 12 days; the second vaccination with what has been 

 desiccated for u days; the third with what has been desic- 

 cated for 10 days, the 4th with what has been desiccated for 

 nine days; the 5th for eight days; the 6th with what has 

 been desiccated for seven days (capable of killing rabbits 

 unprotected by previous inoculation with weaker vaccine) ; 

 the yth (still stronger) with what has been desiccated for six 

 days; the 8th for five days; the Qth for four days; the loth 

 and the last vaccination with the vaccine prepared from 

 spinal marrow which has remained only for three days in 

 the glass jar. Pasteur stops here. He never vaccinates men 

 with the vaccine which is quite virulent. But he believes men 

 vaccinated 10 times with the graduated vaccines can be ino- 

 culated with perfect safety with the virulent vaccines, that is, 

 those made with two and one day's desiccated spinal marrow, 



