HISTORICAL 1 7 



milk and cheese, and suggested that putrefaction and disease 

 were due to minute micro-organisms a contagium animatum or 

 living cause by which disease was produced and transmitted. Hi i 

 discoveries, however, were received with scepticism, much a,s 

 were at first those of Pasteur, the modern father of bacteriology. 



In 1683, Anthony van Leeuwenhoek, a learned linen-weaver 

 of Delft, in Holland, wrote a series of interesting letters to 

 the Royal Society of London, describing observations of 

 bacteria and other minute living organisms, which he made 

 through a microscope of his own manufacture, the grinding 

 and polishing of lenses, which he had learned in his youth, 

 being one of his hobbies in later life. In one of these letters 

 he says : "I saw with great astonishment, especially in the 

 material mentioned (the emulsion of tartar from the teeth) 

 that there were many tiny animals which moved about in a 

 most amusing manner; the largest of these showed the 

 liveliest and most active motion, moving through the water 

 or saliva as a fish of prey darts through the sea ; they were 

 found everywhere, although not in large numbers." 



Leeuwenhoek was content merely to record his interesting 

 discoveries, and did not attempt to found any theories of the 

 causation of disease, putrefaction, and decay upon them ; but 

 other writers who followed him did so, notably the great 

 naturalist Linnseus, and later a learned Viennese physician, 

 Marcus Antonius Plenciz, who, in 1762, propounded a germ 

 theory as the cause of these processes, believing that each 

 infective disease was caused by its own specific germ, and that 

 decomposition of organic substances was similarly brought 

 about. A farther advance, especially in the classification of 

 these minute organisms, was made in 1786, by the Danish 

 biologist, Otto Friedrich Miiller, who introduced many of the 

 terms still in use at the present day, e.g. Vibrio, Bacillus, 

 Spirillum, Proteus, and the like. Other workers, notably 

 Ehrenberg in 1836, and Cohn in 1875, continued the work of 

 discovery and classification ; but it is to the extraordinary in- 

 dustry and genius of Louis Pasteur, one of the greatest 

 scientists of the nineteenth century, that modern bacteriology 

 practically owes its existence. 



Pasteur was born in 1822 at Dole in France, and those who 

 are interested in the advance of science would be well repaid 

 by reading the life story of this great man. 1 It is a record of 

 enormous difficulties and discouragements, and bitter opposition 

 on the part of his so-called scientific opponents, overcome by 

 patient and unremitting industry, lit up by the insight of 



1 Louis Pasteur : His Life and Labours. By his son-in-law. Paris, 

 1883. Translated by Lady Claud Hamilton. London, 1885. 



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