PARASITES 425 



optimum temperature, 37C., or 98%F., the temperature of 

 human blood), they retain their virulence, or disease-causing 

 power, and will speedily cause the death of a susceptible ani- 

 mal if injected into its body. 



491. Methods of Prevention and Cure. Since the dis- 

 covery of a method of preventing this disease was an event of 

 unusual importance in the history of medicine, you will be 

 interested in knowing something of the circumstances which 

 lead to its discovery. The great 

 "Father of Bacteriology," Louis 

 PASTEUR, discovered the principle 



A B 



FIG. 273. A. Bacillus anthrax. B. The same with spores. 



involved in the method in the year 1880 and perfected the 

 method of preventing anthrax during the following year. 

 After ROBERT KOCH had established beyond all possible doubt 

 that Bacillus anthracis is the specific cause of the disease 

 anthrax, PASTEUR turned all his powerful energies and his 

 genius to the study of infectious diseases. 



At this time, anthrax was known and dreaded all over the 

 world and in some years it had caused a loss in France alone 

 of 20,000,000 francs, or 4,000,000 dollars. The burden of the 

 scourge fell heavily upon the peasants or farmers, many of 

 whom had suffered the loss of their entire flocks. Pasteur, 

 some years before, had been of great service to the peasants of 

 his country and the world by showing them how to avoid 

 the terrible silk-worm diseases which had nearly ruined the 

 silk industry of the country and he now longed to find some 

 method of combatting anthrax. He had in his laboratory 

 many cultures of different kinds of pathogenic bacteria and 

 among these were cultures of the bacteria that cause the com- 



