2 BACTERIOLOGY. 



admit of the possibility of studying, or even detecting, the micro- 

 organisms which are now known to be associated with certain 

 diseases ; and it is not surprising that his teachings did not at the 

 time gain much attention. They were destined, however, to receive 

 a great impetus from the discoveries which emanated from "the 

 father of microscopy." 



Antony van Leeuwenhoek had learned as a youth to grind and 

 polish lenses, and later in life employed his spare time in constructing 

 microscopes, and in conducting those researches which have made 

 for him a name which is familiar to all microscopists. His researches 

 were published in a series of letters to the Royal Society. In 1675 

 he described extremely minute organisms in rain-water, well-water, 

 infusions of pepper, hay, and other vegetable and animal substances, 

 in saliva, and in scrapings from the teeth ; and, further, he was 

 able to differentiate these minute living things by their size, their 

 form, and the character of their movements. In 1683 these 

 discoveries were illustrated by means of woodcuts, and there can be 

 little doubt, from the drawings of these micro-organisms, that they 

 are intended to represent leptothrix filaments, vibrios, and spirilla. 

 Indeed, we can almost recognise these micro-organisms as bacteria 

 from Leeuwenhoek's graphic descriptions, apart from his figures. 

 They were described as moving in the most characteristic manner, 

 progressing with great rapidity, or spinning round like a top, and 

 so excessively minute that they were only perceived with great 

 difficulty. The smallest forms could hardly be examined individually ; 

 but, viewed en masse, they closely resembled a swarm of gnats or 

 flies. In another communication, published in 1692, he gives 

 some idea of the size of these animalcules by stating that they 

 were a thousand times smaller than a grain of sand. Others 

 which were, comparatively speaking, of considerable length, were 

 characterised by their peculiar mode of progression, bending and 

 rolling on themselves movements which, he adds, created both 

 delight and astonishment in the mind of the observer. Leeuwenhoek 

 himself was not disposed to believe in the possibility of such 

 organisms being found in the blood in disease; but as soon as he 

 had proved the actual existence of such minute creatures, theoretical 

 physicians were not wanting who at once attributed various maladies 

 to their agency. Among these, Nicholas Andry is made conspicuous 

 by his work published in 1701. Andry classed the minute organisms 

 discovered by Leeuwenhoek as worms. 



In 1718 Lancisi believed that the deleterious effect of the air of 

 malarial districts depended upon animalcules, and others considered 



