1 66 BACTERIOLOGY. 



As a result of these experiments an idea arose 

 that by preventive inoculation with attenuated 

 virus all communicable diseases would in time be 

 eradicated ; but this does not follow, for all com- 

 municable diseases do not confer immunity after 

 a first attack, and in some cases the very reverse 

 is believed to occur. Thus erysipelas of the 

 face leads to an increased liability to subsequent 

 attacks of the same disease. Again, the occurrence 

 of one disease is stated to induce a liability to 

 others ; small-pox and typhoid fever are regarded 

 as predisposing to tuberculosis ; so that the 

 principle of preventive inoculation does not apply 

 in these cases, and its effect would probably tend 

 rather to deleterious results than otherwise. Even 

 with regard to the prevention of anthrax, Pasteur s 

 researches were opposed and criticised. Koch 

 investigated the subject, and came to the con- 

 clusion that the process did not admit of practical 

 application, chiefly on the ground that as immunity 

 only lasted a year, the losses from the vaccination 

 process would be as great or even greater than 

 from the spontaneous disease ; further, there was 

 danger in disseminating a vaccine of the strength 

 required to be effectual. Chauveau proved that 

 the attenuation was due to the temperature, and 

 not to the prolonged effect of oxygen. By keeping 

 cultivations at 42 43 C. in vacua, the virulence was 

 found to disappear in twenty- four hours, and by 

 keeping cultivations at a low temperature with free 



