210 BACTERIA IN DAILY LIFE 



In experiments carried out on animals this im- 

 munity to bee poison has been also induced by 

 repeated application of the irritant. It was for- 

 merly generally supposed that the irritant nature 

 of a bee's sting was due to the presence of formic 

 acid ; but inasmuch as bee poison can retain its 

 poisonous character in spite of being submitted to 

 heat, which would effectually volatilise the formic 

 acid present, this assumption must be abandoned, 

 and opinion is more inclined now to regard this 

 irritant substance as partaking of the nature of an 

 alkaloid. 



Before closing this brief review of some of the 

 most recent discoveries which have been made in 

 the domain of immunity, we must mention some 

 extremely suggestive and important researches 

 on the poison of tetanus, or lock-jaw, which have 

 emanated from Dr. Roux's laboratory at the Institut 

 Pasteur in Paris. 



It will perhaps be remembered that Pasteur, 

 when working at hydrophobia, experienced the 

 greatest difficulty in exciting rabies in animals with 

 certainty, and that it was only when the fact of its 

 being a disease which essentially affects the nervous 

 system of the animal was taken into account that 

 it occurred to him to cultivate the virus in the 

 medium for which it had seemingly the greatest 

 affinity, viz. the nervous tissue of an animal ; it was 



