THE MICROSCOPE. 3 



one. A passage from Varro (116-27 B. C.) reads 

 as follows: "There are swampy places in which 

 grow animals never so small which may not be 

 recognized by the eye, and which gain access to the 

 body through the air and bring about severe 

 diseases.* 7 



The discovery and use of the compound micro- The 



.. V , -. ,, Microscope. 



scope in the seventeenth century disclosed the 

 reality of the minute living forms which had been 

 suspected so often. Kircher, with his first crude 

 microscope (1646), examined the tissues of va- 

 rious diseases, and was the author of many the- 

 ories as to their etiology. It is now believed that 

 the magnification of Kircher's microscope was so 

 small that many of the "worms" which he saw 

 were really larger fungous cells and in some in- 

 stances the as yet unidentified blood and pus cells. 

 Leeuwenhoek (1632-1723), a Dutch naturalist, 

 with his compound microscope magnifying 1,000 

 diameters, observed accurately many microscopic 

 forms, but made no application of his discoveries 

 to medical problems; nevertheless, such applica- 

 tion was not wanting, and the succeeding century 

 and a half saw such voluminous descriptions of 

 microbes, so many contradictory theories and 

 statements concerning their relationship to in- 

 fections, that the "infinitesimally small" fell into 

 disfavor in many quarters as the causes of diseases. 

 The attractions and reasonableness of the theory, 

 however, were such that it continued to gain ex- 

 ponents, and in the early part of the nineteenth 

 century reached a degree of definiteness. In 1855, 

 the great French physician, Bretonneau, affirmed 

 that a specific germ was the cause of every con- 



