AND PREVENTION OF PHTHISIS. 401 



it. The enormous care necessary in such experiments, 

 and, indeed, in the use of instruments generally, has 

 not yet, I fear, been universally realised by medical 

 men. With a care worthy of imitation, Cornet steril- 

 ised the instruments with which his dust was collected, 

 and also the vessels in which it was placed. 



The cultivation of the tubercle bacilli directly from 

 the dust proved impracticable. Their extraordinary 

 slowness of development enabled other organisms 

 weeds of the pathogenic garden which were always 

 present, to overpower and practically stifle them. 

 Cornet, therefore, resorted to the infection of guinea- 

 pigs with his dust. If tuberculosis followed from such 

 inoculation, a proof of virulence would be obtained 

 which the microscope could never furnish. The dust, 

 after being intimately mixed with a suitable liquid, 

 was injected into the abdomen of the guinea-pig. For 

 every sample of dust, two, three, four, or more animals 

 were employed. In numerous cases the infected animal 

 died a day or two after inoculation. Such rapid deaths, 

 however, were not due to the tubercle bacillus, which, 

 as already stated, is extremely slow of development, but 

 to organisms which set up peritonitis and other fatal 

 disorders. Usually, however, some of the group of 

 guinea-pigs escaped this quick mortality, and, to per- 

 mit of the development of the bacilli, they were allowed 

 to live on thirty, fort}', or fifty days. The survivors 

 were then killed and examined. In some cases the 

 animals were found charged with tubercle bacilli, the 

 virulence of the inoculated matter being thus estab- 

 lished. In other cases the organs of the guinea-pigs 

 were found healthy, thus proving the harmlessness of 

 the dust. 



It must here be borne in mind that the bacilli 

 mixed with Cornet's dust must have first floated in the 



