Page:The growth of medicine from the earliest times to about 1800.djvu/404

 arrangement in the eyes of insects; he made original investigations into the origin and mode of development of several species of the lower organisms; he was the first to observe the canaliculated mode of construction in bone, and he also noted the existence of the so-called bone-corpuscles (afterward rediscovered and more accurately described by Purkinje); he discovered the striated condition of the bundles of muscular fibres, and was also the first person to teach the doctrine that the growth of muscles is effected by an enlargement of the primitive bundles of fibres and not by a multiplication of these structures; he taught further that muscle-substance consists of numberless small spheres; he was the first to describe the crystalline lens as a structure composed of fibres which are arranged in layers or sheets; in association with Guillaume Molyneux he studied, under the microscope, the speed with which the blood-current travels in the blood-vessels; he made valuable observations on the nature of the spermatozoa; and, finally, the very first studies in bacteriology appear to have been made by Leeuwenhoek. As a result of his discovery of "round, rod-shaped, thread-like and corkscrew-shaped bacteria" between the teeth of a human being, the theory was set forth that probably many diseases owe their origin to such "little animals."

The same idea, as will be shown farther on, occurred to the distinguished medical practitioner of Verona, Italy,—viz., Fracastoro,—one hundred years earlier (1546). Leeuwenhoek, it should here be stated, possessed a very great advantage over his rivals in the field of minute anatomy, for he was in the habit of using, in his investigations, microscopes which he himself had made, and which magnified from 160 to 270 diameters, whereas those utilized by the others were capable of magnifying, at the maximum, only 143 diameters. While a large part of the work which he performed shows plainly that he was a skilful and careful anatomist and endowed with good mental powers,