SWAMMERDAM, MALPIGIII, E^AUMUE, ETC. 133 



animals (Volatilia), a division which was accepted till Gessner's 

 time. 



With the decline of the sciences, natural history also fell into 

 oblivion. The mind of man, fettered by the belief in authority, felt 

 in the middle ages no need for an independent contemplation of 

 Nature. But the writings of Aristotle and Pliny found an asylum 

 within the walls of the Christian cloisters, which preserved the 

 germs of science developed in Heathendom from complete extinc- 

 tion. 



In the course of the middle ages, first the Spanish bishop, Isidor 

 of Seville (in the seventh century), and later Albertus Magnus 

 (in the thirteenth century) wrote works on natural history ; but it 

 was not until the renaissance of the sciences of the sixteenth century 

 that the works of Aristotle again came to the fore, and the desire 

 for independent observation and research was also roused. Works 

 like those of C. Gessner, Aldrovandus, Wotton, testified to the newly 

 awakening life of our science, whose scope was continually being in- 

 creased by the discovery of new worlds. 



The next century, in which Harvey discovered the circulation of 

 the blood, Keppler the revolution of the planets, and Newton's law 

 of gravitation formed the beginning of a new era in physics, 

 was also a fruitful epoch for Zoology. Aurelio Severino wrote his 

 "Zootorniu democritrea" (1645), a work which contained anatomical 

 drawings of various animals, more for the use and advancement of 

 human anatomy and physiology. Swammerdam in Leyden dissected 

 the bodies of Insects and Molluscs, and described the metamorphosis 

 of the Frog. Malpighi in Bologna and Leeuwenhoek in Delft 

 applied the invention of the microscope to the examination of 

 tissues and the smallest organisms (animals from infusions). The 

 latter discovered the blood corpuscles, and first saw the transverse 

 striations of muscular fibres. The spermatazoa also were discovered 

 by a student, Hamm, and called, on account of their movements, 

 sperm-animals. The Italian Redi opposed the spontaneous genera- 

 tion of animals in putrefying matter, proved the origin of Maggots 

 from Flies' eggs, and supported Harvey's famous expression, " onme 

 vivum ex ovo." In the eighteenth century the knowledge of the 

 life-history of animals was enormously enriched. Investigators such 

 as Reaumur, Rb'sel von Rosenhof , De Geer, Bonnet, J. Chr. Schaeffer, 

 Ledermiiller, etc., discovered the metamorphosis and life-history of 

 Insects and native aquatic animals, while at the same time, by 

 expeditions into foreign lands, a great number of animals from other 



