2l8 BACTERIOLOGY. 



it. After some days the colonies of B. icteroides form a sort of con- 

 stellation around the mould, the most abundant development taking 

 place in the immediate neighborhood of the latter. This observa- 

 tion was experimentally verified with six species of moulds (not 

 named) " accidentally isolated " in the laboratory, all of which proved, 

 although in different degrees, capable of favoring the revivification 

 .and multiplication of the yellow fever germ. To this singular 

 symbiotic relation Sanarelli is inclined to attribute the ready domi- 

 ciling of the disease on shipboard and its connection with warmth, 

 moisture and darkness, conditions which, by directly favoring the 

 germination of moulds, indirectly favor B. icteroides. 



In some brief notes upon the resistance of the germ to physical 

 and chemical agents it is stated that, by exposure of broth cultures 

 to 55, the germ is killed in about twenty minutes, and that it is in- 

 stantly destroyed by a temperature of 65. Dry heat at i io-i25 is 

 speedily fatal, and exposure for one hour aud ten minutes at 100 

 also suffices to destroy vitality. Considerable resistance is shown to 

 desiccation, a result of evident practical importance. In sea water 

 the bacillus shows great vitality, surviving in the sterilized brackish 

 water of the La Plata for upwards of ninety days. 



Sanarelli's third memoir is devoted to a consideration of immunity 

 and serum therapy. The serum obtained from the bodies of yellow 

 fever victims causes agglutination of B. icteroides, although the in- 

 tensity of the reaction is said to be quite variable. t This serum does 

 not exert any protective power in inoculated animals. Serum from 

 a convalescent provoked a tardy agglutination and manifested a 

 slight preventive power. 



An attack of yellow fever in man confers some degree of im- 

 munity against a second attack, and hence it would seem as if it 

 might be possible in some way to vaccinate animals against the 

 disease. Attempts to produce immunity in the rabbit failed on ac- 

 count of the excessive sensibility of this animal to the yellow fever 

 virus, and the same difficulty prevented the use of the goat and the 

 sheep. The work upon immunization was mainly limited, therefore, 

 to experiments upon the guinea-pig, the dog and the horse. In all 

 these animals immunization is an unusually difficult and laborious 

 task. While it is possible to immunize a guinea-pig against cholera 

 or typhoid fever in from two to three months, it needs six to seven 

 months of assiduous and delicate work to vaccinate this animal 

 against yellow fever. Dogs may be immunized somewhat more 

 readily, but never become tolerant of large doses of toxin. Horses 

 are treated first with small doses (5-10 c.c.) of a filtered culture of the 



