22 MANUAL OF BACTERIOLOGY. 



During the same period similar ideas were ad- 

 vanced by Dr. Oliver Wendell Holmes in the United States. 

 His paper on " The Contagiousness of Puerperal Fever " 

 appeared in 1843. A lively controversy lasting several 

 years was provoked, in which Holmes defended his position 

 with great vigor. His admirable literary style served him 

 effectively. 1 



In the first half of the nineteenth century, with improved 

 microscopes, knowledge of minute living things grew 

 rapidly, chiefly with respect to infusoria and other relatively 

 large forms. In 1840 Henle described the part played by 

 microorganisms in producing disease in terms surprisingly 

 in accord with views held at the present time. His deduc- 

 tions were based almost entirely on knowledge of the gen- 

 eral nature, spread and course of infections. So too, 

 Villemin anticipated the discovery of the bacillus of tuber- 

 culosis, for he transmitted the disease to animals, by inocu- 

 lating them with material from cases of tuberculosis in 

 man. 



The key to exact knowledge of the microorganisms of 

 disease was finally discovered in the study of fermentation. 

 No better illustration could be found of the possible value to 

 mankind which may lie in any addition whatever to the 

 common stock of facts. The study of bottles of bad-smell- 

 ing broth would have seemed, fifty years ago, a most un- 

 promising beginning for the discovery of the causes of 

 cholera, plague, and the like, or for an antitoxin for diph- 

 theria. 



Studies on Fermentation and Spontaneous Generation. 

 Two observers (Schwann, Cagniard-Latour, 1837) almost 

 simultaneously stated the proposition that yeast cells were 

 living organisms, and that the fermentation of solutions of 

 sugar was clue to their growth. From this time ensued 



1 See Medical Essays, O. W. Holmes, Houghton, Mifflin & Co., 1889. 



