268 A SHORT HISTORY OF SCIENCE 



the same obscurity as about that of the telescope. Simple micro- 

 scopes such as "magnifiers," burning glasses, spectacles, and other 

 lenses, had long been known, - - some of them from antiquity, 

 but the compound microscope, which consists of two lenses or 

 combinations of lenses so placed as to cooperate in the produc- 

 tion of one highly magnified image of a near and minute object (the 

 telescope doing the same for large and distant objects), first ap- 

 pears about 1650. Some of the earliest microscopists are Kircher, 

 Leeuwenhoek, Malpighi, and Grew. The two former apparently 

 saw with the microscope and made drawings of bacteria, besides 

 many other micro-organisms and cellular structures. The two 

 latter are the founders of microscopic anatomy, Malpighi of that 

 of animals, Grew of that of plants. Malpighi's work is especially 

 notable, since he for the first time actually observed the passage of 

 blood cells from arteries to veins, and that in 1661 only four years 

 after Harvey's death. Malpighi's name is also familiar to students 

 of human anatomy and physiology in connection with those parts 

 of the kidneys and the spleen which bear his name. The versatile 

 and accomplished Englishman Dr. Robert Hooke (1635-1703), who 

 flourished in this century and did ingenious, extensive, and often 

 remarkable work at the basis of almost every branch of modern 

 science, was the first to discover by the microscope the cellular 

 structure of living things. Hooke was one of the original members 

 of the Royal Society, with which Leeuwenhoek also corresponded. 



The most remarkable fact connected with the invention of the 

 compound microscope is that, because of its physical imperfec- 

 tions, and in spite of some use as just described, it was virtually 

 abandoned for almost a century and a half, and only re-introduced 

 after the invention and perfection of the achromatic objective in the 

 first quarter of the nineteenth century. The truth appears to be 

 that owing to excessive spherical and chromatic aberration the 

 compound microscope of the seventeenth and eighteenth centuries 

 was of limited value, and that microscopists often preferred the 

 less powerful, but more perfect, simple microscope. 



The manometer was apparently first used by Stephen Hales, 

 who measured with it the blood pressure of a horse, the root pres- 



