Microscopes 29 



former in the manner of a compound microscope. He provided a lamp 

 for illumination and a bull's-eye condenser for intensifying the light. His 

 microscope had magnifications of 14 to 42 diameters (Fig. 2). He 

 studied many types of natural objects, and from his investigations of 

 cork he saw minute, hollow, boxlike structures to which he first applied 

 the word cell. 



Marcello Malpighi (1628-1694), an Italian scientist and physician, is 

 considered the father of histology because he systematically based his 

 research on the use of magnifying apparatus in his studies of animals 

 and plants. His studies included the detailed structure of lungs, kidneys, 

 spleen, and other organs, the capillary circulation in frogs, and the cellu- 

 lar structure and anatomy of different plants. 



Nehemiah Grew (1628-1712), an English physician, microscopically 

 studied plants and carefully described the cells, tissues, organs, and ves- 

 sels in plants. Malpighi and Grew described the microscopic anatomy of 

 plants so well that it was over a century before any important additions 

 were made to their work. 



Jan Swammerdam (1637-1680), a Dutch physician and student of 

 Nature, studied the anatomy of lower animals by dissection and injec- 

 tions, and his results were unequalled for over one hundred years. He 

 showed a remarkable mastery of the most complicated details in the 

 many lower animals which he dissected. 



The first binocular microscope was designed by Rheita in 1645, two 

 microscopes were held together by three links at the eye end and two 

 links at the specimen end. This arrangement accommodated people who 

 differed as to distance between the eyes and permitted the use of both 

 eyes in viewing objects. 



Bonannus improved the microscope in 1691 and developed a hori- 

 zontal type which included a source of light, a condenser to concentrate 

 light, and a rack and pinion mechanism for more efficient focusing 

 (Fig. 3). 



Wilson, about 1710, developed a screw-barrel type of microscope (Fig. 

 4) which was made of ivory and had a handle. The body had threads 

 on the observing end into which lenses of different magnifying powers 

 might be placed. The opposite end contained a condensing lens to con- 

 centrate light. The specimen was pushed against a spring for focusing. 

 A Wilson type of microscope was received at Harvard College in 1732 

 and may have been one of the first compound microscopes used in 

 American colleges, although simple microscopes probably were used 

 earlier. 



