Chapter 2 



MICROSCOPES— EARLY AND PRESENT DAY 



Because so much scientific progress of the past, present, and future 

 has been and is dependent upon the development and use of the micro- 

 scope, it seems desirable that an understanding of the history of micros- 

 copy, as well as a brief understanding of modern microscopes, should be 

 attempted. No elaborate details can be given, and all contributors to 

 improvements of microscopes cannot be mentioned. The various stages 

 in the development of microscopes illustrate the scientific method. 

 Since problems presented themselves which had to be solved, working 

 hypotheses for their solution were proposed, data were collected and 

 experiments were performed, and finally conclusions were drawn and 

 the particular problems were solved, or if not completely solved the 

 additional information secured may have led other workers to come 

 nearer the true solution. 



It is unknown who invented the first simple microscope which was 

 really a magnifying glass with a lens thicker at the center than at the 

 edge. Layard excavated a rock crystal at Nineveh which may have been 

 a "lens" of the eighth century B.C. Even though burning glasses were 

 used, probably magnifying glasses were not used extensively until the 

 invention of spectacles at the end of the thirteenth century. The early 

 simple microscopes (magnifying glasses) were commonly called ''flea 

 microscopes^^ because a flea was a specimen commonly investigated. Ac- 

 cording to present information, Anthony van Leeuwenhoek (1632-1723), 

 a Dutch microscopist, developed a simple microscope (about 1673) by 

 mounting a lens between two flat pieces of metal and adding a pivoted 

 point for holding the specimen (Fig. 1). He ground lenses which had 

 magnifications of 40 to 160 diameters. With his lenses he studied bac- 

 teria, protozoa, molds, red blood corpuscles, plants, animals, the circu- 

 lation of blood in the tadpole tail, etc. 



A compound microscope, was invented by Zaccharias Janssen and his 

 son Hans about 1590 in Middleburg, Holland. These spectacle makers 



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