TEXT-BOOK OF BACTERIOLOGY. 211 



The question of attenuation has not only a theoretical, but also a 

 practical interest, since it stands in immediate connection with the 

 question of artificial immunity. 



We are aware that sheep and cattle which it is intended to in- 

 oculate protectively on Pasteur's system, are first infected with a 

 \\vaker material (premier vaccin) and after some days with the 

 st ronger material (deuxieme vaccin). As a rule, a more or less vio- 

 lent inoculation fever ensues; when this is over, one can inoculate 

 the animals with material of full virulence without its harming 1 

 them. Against intestinal anthrax they are, however, not perfectly 

 safe, as has been shown by Koch, GalTky, and Loffler, and this is 

 one of the reasons which make it undesirable to unconditionally 

 recommend the adoption of protective inoculation as a regular 

 practice. 



No other species of bacteria has been so carefully studied as the 

 anthrax bacillus with regard to attenuation and immunity, sepa- 

 rately as well as in their mutual relations to each other. For both, 

 quite a number of other procedures have been recommended be- 

 sides the one just mentioned, which, however, is the only one that 

 has any importance for ordinary practical use. 



According to Toussaint, virulent anthrax bacilli are rendered 

 non-poisonous by adding \% of carbolic acid to anthracic blood; 

 Chamberland and Roux obtained the same result by breeding in 

 food solutions containing from -^\-$% to -faf, of bichromate of potas- 

 sium ; Lubarsch and Petruschky found the attenuation took place 

 when the bacilli are compelled to exist in the bodies of non-inocula- 

 ble animals of frogs, for instance; Chauveau discovered that an 

 increased pressure of six or eight atmospheres produced the same 

 effect; Arloing was able to diminish virulence by direct exposure 

 to sunlight. 



Chamberland and Roux, to obtain artificial immunity, employed 

 sterilized cultures of virulent bacteria instead of attenuated bac- 

 teria; Hueppe and Wood performed a successful protective inocu- 

 lation by means of a perfectly harmless species of bacteria, scarcely 

 allied to the anthrax bacillus; Hankin obtained from anthrax cul- 

 tures a substance which granted immunity an albuminoid body 

 of peculiar qualities ; Wooldridge, lastly, took aqueous extracts rich 

 in albumin, from the thymus gland and the parenchyma of the 

 testicle of healthy animals, and with this obtained protection 

 against anthrax. 



This is the proper place to consider certain discoveries which 

 a iv more or less connected with the question of immunity. Behring 

 made the rat, which is naturally refractory to anthrax infection, 



