218 MICROBES, FERMENTS, AND MOULDS. 



conditions. If they settle on a child's tender throat, 

 predisposed for their reception by slight inflammation, 

 they develop there with frightful rapidity, and 

 produce croup, and then diphtheria, which is soon 

 fataL Nageli calculates that their number may be 

 doubled within twenty minutes. The plant, of which 

 the activity is increased by its culture in the person of 

 one patient, may be expelled with the breath so as 

 to infect another individual. And just as there are 

 different degrees of activity in the plant, so the spores 

 may be more or less contagious, and those of malig- 

 nant diphtheria are more to be feared than those of 

 the ordinary diphtheritic angina. 



When we consider the remedies to be employed 

 against the ravages of this cruel disease, it should 

 first be observed that the only effect of the operation 

 of tracheotomy, which is successful in barely a third 

 of the cases, is to admit air into the child's lungs. 

 Its first curative effect, therefore, consists in saving the 

 child from the asphyxia by which it is threatened, 

 and in giving time to apply remedies, but another 

 explanation is necessary when this operation alone is 

 enough to effect a cure. Pasteur has shown that pro- 

 longed contact with the air produces a real attenuation 

 of virulent microbes. Wood and Formad have estab- 

 lished similar facts, for when the false membranes of 

 croup procured at Ludington had been exposed to the 

 air for several weeks, until they were completely 

 desiccated, they became perfectly inert, notwithstand- 



