172 BIOLOGY AND ITS MAKERS 
The strong features of this veteran of research are shown 
in the portrait, Fig. 50, which represents him at the age of 
seventy. 
In 1847 he was called to the University of Wiirzburg, 
where he remained to the time of his death. From 1850 to 
1g0o, scarcely a year passed without some important contri- 
bution from Von Koelliker extending the knowledge of his- 
tology. His famous text-book on the structure of the tissues 
(Handbuch der Gewebelehre) passed through six editions from 
1852 to 1893, the final edition of it being worked over and 
brought up to date by 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 completely over the ground of the vast accumulation of 
information regarding the nervous system which an army 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 Max 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 phases: 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 
