172 BIOLOGY AXD ITS MAKERS 



The strong features of this veteran of research are shown 

 in the ])orlrait, Fig. 50, which represents him at the age of 



seventy. 



In 1S47 he was called to the University of Wurzburg, 

 where he remained to the time of his death. From 1850 to 

 iQoo, scarcely a year passed without some important contri- 

 bution from \'on Koelliker extending the knowledge of his- 

 tologv. His famous text-book on the structure of the tissues 

 {tlandbuch dcr Geivebclehre) joassed through six editions from 

 1852 to 1893, ^^^^ ^'^"'^^^ edition of it being worked over and 

 brought up to date b}- this extraordinary man after he had 

 passed the age of seventy-five. By workers in biology this 

 will be recognized as a colossal task. In the second volume 

 of the last edition of this work, which appeared in 1893, he 

 went com])letely over the ground of the vast accumulation of 

 information rerardinsr the nervous svstem which an armv of 

 gifted and energetic workers had produced. This was all 

 thoroughly digested, and his histological work brought down 

 to date. 



Schultze. — ^The fine observations of ^lax Schultze (1825- 

 1874) may also be grouped with those of the histologists. 

 We shall have occasion to speak of him^ more particularly in 

 the chapter on Protoplasm.. He did memorable service for 

 general biology in establishing the protoplasm doctrine, but 

 many of his scientific memoirs are in the line of normal 

 histology; as, those on the structure of the olfactory mem- 

 brane, on the retina of the eye, the muscle elements, the 

 nerves, etc., etc. 



Normal Histology and Pathology. — But histology has 

 two }:)hases: the investigation of the tissues in health, which 

 is called normal histology; and the study of the tissues in 

 disease and under abnormal conditions of development, 

 which is designated pathological histology. The latter divi- 

 sion, on account of its importance to the medical man, has 



