ATTENUATION OF VIRUS. 201 



INOCULATION EXPERIMENTS. In order to cause death of ani- 

 mals by inoculation of the bacillus of anthrax, the pure culture, or 

 anthracic blood, must be injected into the subcutaneous tissue, into 

 the circulation, or the virus may be transmitted by inhalation or 

 by feeding. Goats, hedgehogs, sparrows, cows, horses, guinea-pigs, 

 and sheep, can be readily infected. Eats are less susceptible. Pigs, 

 dogs, cats, white rats, and Algerian sheep are immune. Frogs and 

 fish have been rendered susceptible by raising the temperature of 

 the water in which they lived. 



ATTENUATION OF VIRUS. By cultivating the bacillus in neu- 

 tralized bouillon at 42-43 C. (107.6-109.4 F.) for about 

 twenty days the infecting power is weakened and animals inocu- 

 lated with it are protected against the disease. A still greater 

 immunity is obtained by inoculating a second time with material 

 which has been less weakened. The animals are then protected 

 against the most virulent form of anthrax, but only for a time. A 

 temperature of 55 C. (131 F.), or treatment with 5 to 1 per cent, 

 solution of carbolic acid deprives the bacilli of their virulence. 

 The virulence of the bacillus is also altered by passing it through 

 different species of animals. 



Woolbridge secured immunity against anthrax in animals by 

 cultivating the bacillus in an alkaline solution at a temperature of 

 37 C. (98.6 F.) for two days. At this time the fluid was filtered 

 and a small quantity of the filtrate injected into the subcutaneous 

 tissue of rabbits, which remained well, and subsequently resisted 

 injection of most virulent authracic blood. 



Hankin (" Immunity produced by an Albuminose isolated from 

 Anthrax Cultures/' British Med. Journal, Oct. 12, 1889), under the 

 guidance of Koch at the Hygienic Institute of Berlin, isolated an 

 albumose from anthrax cultures which, when injected into rabbits 

 and mice in small quantities, rendered these animals immune against 

 the most virulent cultures. The albumose was prepared from the 

 cultures by precipitation with absolute alcohol, the precipitate was 

 well washed in this liquid to free it from ptomaines, since it is 

 known that all such substances are soluble in alcohol. After the 

 addition of alcohol it was filtered off and dried, then redissolved, 

 and filtered through a Chamberland's filter. Four rabbits were 

 inoculated with virulent anthrax spores and three of them received 

 an injection of albuminose into the ear-vein at the same time; the 

 latter recovered, while the remaining animal not thus protected 

 died in about forty-eight hours of anthrax. In another experi- 

 ment, ten mice were each injected with the millionth part of their 

 body-weight of anthrax albuminose and with active vaccine at the 

 same time. Of these, three died after 108 to 116 hours; the others 

 recovered. Three others had only the two-milliouths of their body- 



