6 BACTERIOLOGY. 



than tlie bacilli themselves. In such cases mere scalding or boiling 

 for a few minutes wiU not sterilise the solution. The bacilli are 

 destroyed, but not their spores; and if the latter remain unhurt, 

 they will germinate, and rapidly multiply. But if, as Tyndall 

 foiind, the boihng be repeated a second and a third time, all the 

 spores will be destroyed ; for in the intervals between the boilings 

 the spores sprout into bacilli, and the bacilli at the next boihng 

 perish ; so that after three or four repeated boilings the infusion is 

 rendered perfectly free from germs. 



While this discussion was occupying the attention of the whole 

 scientific world, some investigators had been again following up the 

 theory of a connection between micro-organisms and disease. 



In 1837 Cagniard Latour and Schwann independently made the 

 •discovery that the yeast plant was a living organism, and the true 

 cause of yeast fermentation. The close analogy between the pro- 

 cesses of fermentation and of certain diseases had long been held; 

 and, therefore, when it was proved that fermentation was due to a 

 micro-organism, fresh advocates appeared in support of the theory 

 that diseases were produced by similar agencies. Boehm, in 1838, 

 described certain organisms in cholera, which was at that time 

 raging in Europe; but the researches of Bassi, who a year 

 previously had discovered the cause of a disease of silkworms, 

 attracted much greater attention. 



Bassi discovered that in this disease extremely minute spores 

 existed on the bodies of the worms, which were conveyed from the 

 sick to the healthy. They destroyed the healthy worms by 

 germinating in their skins and growing into their bodies. These 

 discoveries may be said to have brought the theory of contagium 

 vivum to Ufe again ; and Henle, in reviewing the facts of the case in 

 1 840, came to the conclusion that the cause of all contagious diseases 

 must be of a living nature, and this he maintained, although he 

 had searched in vaecine and small-pox lymph, in the desquamation 

 of scarlet fever, and in other diseases without success. 



Bassi's discovery and Henle's doctrine encouraged a number of 

 investigators, and remarkable results followed. In favus, in herpes 

 tonsurans, in pityriasis versicolor, fungus threads and spores were 

 found, and were regarded as being of etiological importance, 

 inasmuch as the morbid lesions corresponded vsdth the growth of the 

 particular fungus. 



Cholera became especially a subject for research. Swaine, 

 Brittan, and Budd found micro-organisms in choleraic dejecta. 

 Davaine described certain monads in the intestinal contents, but no 



