22 Introduction 



which a body in the course of decomposition communicates 

 to other matter whose elements are connected by a very 

 feeble affinity. 



Pasteur was the first to prove that fermentation is an 

 ordinary chemic transformation of certain substances, tak- 

 ing place as the result of the action of living cells, and 

 that the capacity to produce it resides in all animal and 

 vegetable cells, though in varying degree. 



In 1862 he published a paper "On the Organized Cor- 

 puscles Existing in the Atmosphere," in which he showed 

 that many of the floating particles collected from the atmos- 

 phere of his laboratory were organized bodies. If these 

 were planted in sterile infusions, abundant crops of micro- 

 organisms were obtained. By the use of more refined 

 methods he repeated the experiments of others, and showed 

 clearly that "the cause which communicated life to his in- 

 fusions came from the air, but was not evenly distributed 

 through it." 



Three years later he showed that the organized cor- 

 puscles which he had found in the air were the spores or 

 seeds of minute plants, and that many of them possessed 

 the property of withstanding the temperature of boiling 

 water a property which explained the peculiar results 

 of many previous experimenters, who failed to prevent 

 the development of life in boiled liquids inclosed in her- 

 metically sealed flasks. 



Chevreul and Pasteur, by having proved that animal 

 solids do not putrefy or decompose if kept free from the 

 access of germs, suggested to surgeons that putrefaction in 

 wounds is due rather to the entrance of something from 

 without than to changes within. The deadly nature of the 

 discharges from putrescent wounds had been shown in a 

 rough manner by Gaspard as early as 1822 by injecting 

 some of the material into the veins of animals. 



III. MEDICAL AND SURGICAL CONTRIBUTIONS; THE STUDY OF THE 

 INFECTIOUS DISEASES. 



Probably the first writing in which a direct relationship 

 between micro-organisms and disease is suggested is by 

 Varro, who says: "It is also to be noticed, if there be any 

 marshy places, that certain minute animals breed [there] 

 which are invisible to the eye, and yet, getting into the 

 system through mouth and nostrils, cause serious disorders 

 (diseases which are difficult to treat)." 



