GENERAL CONSIDERATIONS 9 



Lister, and a growing school of biologists who pushed back farther and 

 farther the organisms supposed to arise de novo. Lower invertebrates, 

 algae and Protozoa, and finally bacteria, one after the other forming the 

 fighting lines of the army of ignorance, now fell back, little by little, 

 before the slow but sure advance of science. 



In connection with this theory of spontaneous generation, a novel 

 conception sprang up with the observations of the French naturalist 

 Buffon in 1749. This conception, expanded by Needham (1750), was 

 a suggestive forerunner of the cell theory outlined by Schleiden and 

 Schwann in 1839-40. The wealth of difi^erent forms of life and the 

 numbers of each type in natural waters in which decomposition was under 

 way, was interpreted by Buffon and Needham as the result of disintegra- 

 tion of animals and plants in water and the resulting liberation of myraids 

 of "organic particles" (BuflFon) of which such animals and plants were 

 composed. 



Protozoology, like cytology, owes its birth and development to the 

 use of the microscope. There has been much discussion and much diver- 

 sity of opinion over the discovery of the microscope, meaning the com- 

 pound instrument, the significant principles of which have been adapted 

 and improved until the beautiful microscopes of today are the outcome. 

 Woodruff (1939) writes: 



Galileo (1610) was the first to use the instrument, — but the first figures 

 ever made with the aid of a compound microscope to appear in a printed 

 book, were by Francesco Stelluti in 1625. But an Englishman, Robert Hooke, 

 was the first to realize to the full the importance of using instruments which 

 increase the powers of the senses in general and of vision in particular, and 

 to express it convincingly in 1665, in a remarkable book: the "Micrographica." 

 Here he described and emphasized for the first time, the "little boxes or 

 cells" of organic structure, and indelibly inscribed the word "cell" in bio- 

 logical literature. (Woodruff, loc. c'll., p. 2.) 



As stated above, the real discoverer of the Protozoa was a Dutch mi- 

 croscopist, Anton von Leeuwenhoek (1632-1723) who, using crude 

 lenses of his own make, was one of the first to apply the microscope to 

 scientific investigation. His contributions to microscopic anatomy and to 

 physiology, inaugurating, as they did, the invaluable services of the 

 microscope in biological research, marked an epoch in the history of 

 science. In a letter to the Royal Society in 1675, Leeuwenhoek wrote that 

 he had discovered 



