HISTORICAL ZOOLOGY 271 



tant role in the advancement of his chosen field of work. He not 

 only studied living forms, but was one of the greatest contribu- 

 tors to the science of paleontology. 



c. Histology 



Bichat (1771-1801) was the founder of histology. His work 

 was of a high order, ranking with that of the physiologist J. 

 Muller and the embryologists Van Baer and Balfour. He 

 directed the attention of biologists to the study of tissues, and, 

 though he did not use a microscope and failed to make out the 

 cellular structures, his investigations led to the modern science 

 of histology. 



The introduction of the microscope added new impetus to the 

 science of the anatomy of tissues, and resulted in the announce- 

 ment of the cell theory by Schwann in 1839, as described in 

 Chapter III (pp. 35-36). Max Schultze (1825-1874), by identi- 

 fying vegetable protoplasm with animal sarcode, reformed the 

 ideas regarding cells. Rudolph Virchow (1821-1903) took up 

 the study of diseased tissues, and helped establish the cell theory 

 as it is understood to-day. 



d. Embryology 



The rise of embryology dates from the time of William Harvey 

 (1578-1667, Fig. 153) and Marcello Malpighi (1628-1694). The 

 former published in 1651 a work descriptive of the embryology of 

 the chick, and of several mammals. Malpighi was further re- 

 moved from the influence of the ancients than Harvey, and his 

 works on embryology are of greater value. His contributions 

 include a detailed description of the development of the chick, 

 illustrated by excellent drawings. 



Previous to the time of Friedrich K. Wolff, embryologists be- 

 lieved in what is known as the preformation theory. According 

 to this theory the embryo exists in miniature within the egg, 

 and during development simply unfolds and expands. From 



