History of Biology. 349 



organs of which it is made up, then of the tissues composing 

 these organs, of the cells, or component parts of the tissues, 

 and, lastly, of the protoplasm or ultimate physi -al basis of 

 life, so in the history of biology the progress has been in 

 all respects similar. 



As, year by year, hundreds upon hundreds of new 

 species of animals and plants were added to the catalogues 

 already in existence, and as naturalists with the help of the 

 microscope and the scalpel dived deeper and deeper into 

 their structure, it soon became a sheer impossibility for one 

 man to master the entire range of biological knowledge a 

 feat easy enough in the days of Aristotle. Division of labour 

 became necessary. One naturalist devoted himself to Botany, 

 another to Zoology, still further specialising* in some par- 

 ticular line research, morphological or physiological, as taste 

 or circumstance dictated. 



Thus Laurent de Jussieu (1748-1836) in Botany and 

 Baron Cuvier (1769-1832) in Zoology laid the foundation- 

 stone of morphology by their classic treatises, Genera Plan- 

 taruui (1789) and Rcgne Animal (1817). About the same 

 time Haller (1708-1777) and Bonnet (1720-1793) esta- 

 blished on a true scientific basis the subject of physiology. 

 With them Biology advanced from being a study of external 

 form and habit to that of internal organisation and function. 

 It was an easy step from that to the study of tissues, a step 

 greatly aided by the continued improvement of the micro- 

 scope. One prominent name, that of Bichat (1771-1802), 

 stands out as the founder of histology, or tissue study, and 

 histogeny, or tissue development, in his Anatomic Generate 

 (1801). 



Research could not, however, rest there. As the physi- 

 cists improved their lenses, the biologists with their help 

 were enabled to analyse tissues into cells. Schleiden (1804- 

 1881) was the first by means of the improved technical 

 appliances to perform that analysis in plants ; a discovery 

 which he followed up by a generalisation to the effect that 



