modern medicine. Though the contributions which 

 have done most to place bacteriology on the footing of 

 a science are those of recent years, still, during the 

 earlier stages of its development, many observations 

 were made which formed the foundation-work for much 

 that was to follow. Before regularly beginning our 

 studies, therefore, it may be of advantage to acquaint our- 

 selves with the more prominent of those investigations. 



Antony van Leeuwenhoek, the first to describe the 

 bodies now recognized as bacteria, was born at Delft, in 

 Holland, in 1632. He was not considered a man of 

 liberal education, having been during his early years an 

 apprentice to a linendraper. During his apprenticeship 

 he learned the art of lens-grinding, in which he became 

 so proficient that he eventually perfected a simple lens 

 by means of which he was enabled to see objects-^f 

 much smaller dimensions than any hitherto seen 4fcth 

 the best compound microscopes in existence at that 

 date. At the time of his discoveries he was following 

 the trade of linendraper in Amsterdam. 



In 1675 he published the fact that he had succeeded 

 in perfecting a lens by means of which he could detect 

 in a drop of rain-water living, motile " animalcules " 

 of the most minute dimensions smaller than anything 

 that had hitherto been seen. Encouraged by this dis- 

 covery, he continued to examine various substances for 

 the presence of what he considered animal life in its 

 most minute form. He found in sea-water, in well- 

 water, in the intestinal canal of frogs and birds, and in 

 his own diarrhoeal evacuations, objects that differenti- 

 ated themselves the one from the other, not only by 

 their shape and size, but also by the peculiarity of 

 motility which some of them were seen to possess. 



