296 INTRODUCTION TO THE STUDY OF FUNGI 



The close study and prolonged investigations of patho- 

 genous species led to important results in the practice of a 

 system of vaccination, which has been adopted not only in 

 anthrax but also in other contagious diseases. It has long 

 been known that in a number of diseases of this class one 

 attack carries some immunity against that particular disease 

 in the future. The process had been employed in smallpox, 

 and it was found that vaccination of a mild form commonly 

 ensured the individual, at least for a lengthened period, against 

 subsequent attacks from the virulent form. It was thought to 

 apply this to animals in the case of anthrax, if a mild form 

 could be obtained for the purpose. In 1880 Greenfield 

 announced the first indication of the modification of anthrax 

 virus, and from that time forward there was a steady advance 

 in the production of a protective vaccinal fluid for anthrax. 

 Pasteur attributed the diminution of the virulence of the 

 bacillus to the action of heat, in the presence of oxygen, but 

 Chauveau contended that heat alone was sufficient. By culti- 

 vating the bacilli successively in a temperature of from 42° 

 to 43° Cent., they were found to lose all their vitality in about 

 six weeks, this loss going on progressively with the rise of 

 temperature. Sheep inoculated with the culture, after twelve 

 days' heating, only succumbed to the extent of one half. 

 After twenty-four days of heating, inoculation did not cause 

 the death of a single animal. After twelve days more, inocula- 

 tion with virulent anthrax blood only caused slight febrile 

 conditions. Absolute protection could only be secured by a 

 second vaccination with the attenuated lymph. It was demon- 

 strated further that the modified action of the bacilli was 

 transmitted to their spores, and that, when produced, these 

 sprouted, not into virulent anthrax bacilli, but into modified 

 anthrax bacilli, suitable for vaccination. 



It follows, then, that when animals are inoculated with a 

 liquid containing bacilli, of which the virulence has been 

 attenuated by culture, carried as far as the tenth generation, 

 their lives are preserved ; they have the disease in a very mild 

 form, and, as a result of this treatment, they are henceforward 

 safe from a fresh attack of the disease, — they are vaccinated 

 af^ainst anthrax. Other methods have been tried for the 



