52 2 ZOOLOGY 



a Frenchman, who gave us the idea of differentiation of parts and 

 division of labor and showed its value; Richard Owen (1804- 

 1892) an Englishman who developed the contrasts of analogy 

 and homology in organs (see §113); Thomas Huxley (1825- 

 189s), who did much to popularize zoology and to introduce the 

 laboratory method into schools; Karl Gegenbauer (1826-1903), 

 whose power of analysis and discrimination have made per- 

 manently available the work of his predecessors ; and the 

 American, E. D. Cope (1840-1897), who added greatly to our 

 knowledge particularly in the comparative anatomy both of liv- 

 ing and fossil forms of vertebrates. 



From the study of the organs interest passed continually to 

 the smaller and smaller units, — tissues and cells. Bichat (i 7 7 1- 

 1801) a brilliant French anatomist studied the tissues of the 

 body, especially the membranes and their function and disorders. 

 While he did not make use of the compound microscope as his 

 successors did he opened up the new field. At this time the 

 microscope had been in use for a half century or more. Its 

 improvement and Bichat's work soon brought about a recogni- 

 tion of the cells of which the tissues are made. Schwann (1810- 

 1882) and Schleiden (1804-1881) conjointly demonstrated that 

 the cell is the essential unit of organization both in plants and 

 animals. This was in 1838. As early as 1809, Lamarck antici- 

 pated this conclusion, but did not have the supporting mass of 

 evidence possessed by Schwann and Schleiden. Cells in plants 

 had been seen by the Englishman, Hooke, as early as 1665. 

 Brown, also an Englishman, described the nucleus in 1833; but 

 during this time no great importance was attached to the facts. 

 In 1861, Max Schultze (1825-1874) was the first to make clear 

 that it is the protoplasm, rather than the cell as such,- that is 

 fundamental. 



From this time on the study of protoplasm and its minute 

 structures, its chemistry, and activities, — cytology — has been 

 one of the most attractive and profitable fields of research. 

 The improvements in the microscope, in sectioning and staining 

 cells, and the like, have made possible some of the most brilliant 

 attacks on the mysteries of life. From these studies we have 

 our knowlege of the nucleus, the chromosomes, the centro- 



