278 



YELLOW FEVER 



disease is more virulent after a prolonged sojourn- 

 ing in the mosquito, was proved beyond all question 

 by the work of 1 899-1 901. But, so far as immun- 

 isation is concerned, few people would submit them- 

 selves to be bitten by an infected mosquito, even 

 with perfect assurance that the germs contained in 

 it were of a low degree of virulence : the urgent 

 need, therefore, was for an immunising serum. In 

 1896, at Flores, Sanarelli discovered the bacilhts 

 icteroides ; and by October, 1897, ne na cl prepared 

 an immunising serum which was able to give a 

 considerable amount of protection to animals. He 

 says of it, in the Annales de IPnstitut Pasteur, 

 October 1897 : — 



" This serum was tried, directly after it had 

 been obtained, on guinea-pigs, against a mortal 

 dose of virulent cultures. Half a cubic centimetre 

 of this serum, injected 24 hours before the dose of 

 virulent cultures, gave immunity. Two centimetres 

 of it succeeded in saving guinea-pigs already ill, 

 even if it were injected 48 hours afterward. These 

 doses are still far from representing the full preven- 

 tive and curative power of the serum, especially if 

 one takes count of the power of the other sera pre- 

 pared up to the present time. . . . 



" Such are the results hitherto obtained by 

 laboratory work on the specific treatment of yellow 

 fever. The preventive and curative power of the 

 serum of the guinea-pig, the dog, and the horse, 

 vaccinated against the bacillus icteroides, should be 

 held as absolutely demonstrated in the case of 

 animals." 



Next year (Annales de llnstitut Pasteur, May 



