68 THE MAIN CURRENTS OF ZOOLOGY 



took on new and important aspects. It is a subject 

 in which all medical students are trained and reveals 

 what may be called the physiological anatomy of the 

 tissues. After the establishment of the cell-theory 

 it became clear that organs do not perform their 

 function as units but through their smaller ele- 

 ments the cells. 



The rise of histology is interesting, but to follow it 

 specifically would involve too great detail. Among 

 the many workers in this field we may select von 

 Koelliker (1817-1905), (Fig. 15), as the typical 

 histologist of the nineteenth century. He published 

 a text-book of Histology in 1857 and, thereafter, for 

 forty years he continued to make contributions to 

 this division of science. His great book on the tissues 

 (Handbuch. der Gewebelehre) passed through several 

 editions from 1 8 70 to 1 897 . It was thoroughly revised 

 and brought down to date in the years 1894-1897. 



The plant histologists, Grew and Malpighi, of the 

 eighteenth century made interesting observations 

 and published many sketches of the microscopic ap- 

 pearance of plant tissues. These sketches, which 

 were faint foreshadowings of the cell idea, can be 

 examined by those sufficiently interested to look 

 up the works of Grew and Malpighi. 



