CHEMICAL RESEARCHES 105 



It must always be remembered that Pasteur was 

 trained as a chemist — was, in fact, a chemist. In after- 

 life he attacked problems proper to the biologist, the 

 physiologist, the physician, the manufacturer ; but he 

 brought to bear on these problems, not the intellect 

 of one trained in the traditions of natural science, 

 medicine, or commerce, but the untrammelled intelli- 

 gence of a richly-endowed mind, ' organized common 

 sense ' of the highest order. After the legal, there is, 

 perhaps, no learned profession so dominated by tradi- 

 tion, by what our fathers have taught us, as the 

 medical ; and the advances in preventive medicine 

 which will ever be connected with Pasteur's name 

 owe at least something to the fact that he was un- 

 fettered by any traditions of professional training or 

 etiquette. Passing from the diseases of the lowest of 

 the fungi to those of a caterpillar, a fowl, a sheep„until 

 he reached those of man himself, it must be acknow- 

 ledged that he approached the art of healing along an 

 entirely new path. 



His first researches were purely chemical — ' On the 

 Capacity for Saturation of Arsenious Acid,' ' Studies 

 on the Arsenates of Potassium, Soda, and Ammonia ' 

 — but he had been early attracted to the remarkable 

 observations of Mitscherlich and others on the optical 

 properties of the crystals of tartaric acid and its salts. 

 Ordinary tartaric acid crystals, when dissolved in 

 water, turn the plane of polarized light to the right ; 

 but another kind of tartaric acid, called by Gay-Lussac 

 racemic acid, and by Berzelius paratartaric acid — as 

 M. Vallery-Radot remarks, the name does not matter, 

 and each is equally terrifying to the lay mind — leaves 

 it unaffected. ' In spite of the different actions of the 

 solutions of these two acids on light, Mitscherlich 

 held their chemical composition to be absolutely 

 identical. 

 This set Pasteur thinking. He repeated the experi- 



