THE STUDY OF STRUCTURE. 331 



taken just at the dawn of the nineteenth century, 

 when Bichat, in his Anatomie Generate (1801) ana- 

 lysed the body into its component tissues, muscular 

 nervous, glandular, connective, and so on. This may 

 be called the beginning of histology, which has now 

 so many devotees. From Bichat's classic we pass 

 to Leydig's foundation of comparative histology 

 (Lehrbuch der Histologie des Menschen und der 

 Thiere, Frankfurt, 1857) a most remarkable work 

 for its date, and it brings us to the modern study of 

 tissues, which has been so much stimulated by im- 

 provements in microscopic apparatus and technique. 

 As the researches of Professor Albert von Kolliker 

 of Wiirzburg extend over a period of sixty years, and 

 over the entire field of animal histology, we could 

 not choose a more fitting or more illustrious repre- 

 sentative of nineteenth-century histological research. 



(4) The Cells. To the scalpel the lens was 

 added ; and then the scalpel was supplemented by the 

 razor (first used by hand and now in a microtome) ; 

 and lens was added to lens to form 3) compound 

 microscope. Thus minute analysis could not remain 

 long at the level of tissues ; these were soon analysed 

 into their component or originative cells, the nucle- 

 ated corpuscles of living matter which form the 

 basis of all organic structure. This step must be 

 especially associated with the work of Schleiden and 

 Schwann, who formulated the " Cell-Theory " in 

 1838-39. With the study of cell-structure hundreds 

 of modern workers are more or less exclusively occu- 

 pied. 



(5) Protoplasm. The fifth and last step in mor- 

 phological analysis, within the limits of biology, is 

 that which passes from the cell as such to a study of 

 the living matter and other substances which com- 



