BACILLUS ICTEROIDES. 291 



respiratory tract, and not through the gastro-intestinal tract, 

 as is commonly supposed. He suggests that moulds may 

 protect Bacillus icteroides and furnish nourishment, especially 

 in damp places like the hold of a ship. The bacillus pro- 

 duces a toxin. Animals immune to yellow fever, or whose 

 susceptibility is not very great, are not affected by this toxin. 

 Sanarelli found that the injection into man of small quantities 

 of a filtered culture of Bacillus icteroides was followed by a 

 typical attack of yellow fever. 



Sanarelli has also prepared a curative serum, which he calls 

 antiamarylic serum. It is not an antitoxin, but only a germi- 

 cide, thus making its administration useless in those cases in 

 which a large amount of toxin has been produced. It must 

 be used early, before any considerable amount of toxin has 

 been elaborated and absorbed. The serum has not, as yet, 

 been tested sufficiently to warrant the expression of a positive 

 opinion as to its curative value. 



Infection : Laboratory experiments and clinical researches 

 have positively established the fact that the mosquito, the 

 variety Anopheles, is the most important, if not the only 

 source or method by which the infection in yellow fever is 

 conveyed. This mosquito bites the yellow fever patient, and 

 then by again biting a well person carries the infecting germ 

 from the sick to the well. There are two periods when the 

 bite of the mosquito is dangerous : first, shortly after it has 

 bitten a yellow fever patient, when its sucking apparatus still 

 contains the germ-laden blood ; second, after the germs have 

 developed sufficiently within the body of the mosquito so that 

 its salivary organs contain the specific germ. In the first 

 case, the course of the disease is a rather mild one, and in the 

 second very severe. One observer asks whether this might 

 not be of some value clinically in producing immunity to 

 yellow fever by a mild attack of the disease. One attack 

 confers positive immunity. 



While a number of investigators have confirmed the claims 

 of Sanarelli that Bacillus icteroides is the specific cause of 

 yellow fever, others are inclined to believe that it is simply 

 one of the many associated organisms so frequently found in 

 the lesions of yellow fever. 



