MODERN BIOLOGY 397 



with such care and reliability as had never been done before; even the division 

 of the nucleus was observed with great accuracy. His ' ' transitory cytoblasts" 

 are chromosomes, although, with the inferior means at his disposal at that 

 time, he was unable either to follow the course of development to the end 

 or to interpret it aright. 



While, then, plant-cytology was making rapid progress, cell research 

 in the animal kingdom was by no means unproductive. Among those who 

 collaborated in the working up of this field of research it is only possible 

 to name a few of the most influential: to begin with, some of Johannes 

 Miiller's pupils, Henle, Reichert, Remak, and Kolliker. 



Jacob Henle was born at Fiirth, near Nuremberg, in 1809, the son of a 

 Jewish merchant who later, with his entire family, adopted Christianity. 

 He studied at Bonn under Miiller, afterwards becoming the latter's prosector 

 in anatomy at Berlin. There, however, he became the victim of political 

 persecution; he was a liberal and a member of the Burschenschaft, with the 

 consequence that, like so many other youths at that time, he was arrested 

 by the scarified Prussian police and after lengthy law-court proceedings was 

 condemned for treason. His scientific reputation, however, saved him from 

 further rigorous treatment; Humboldt, among others, interceded for him, 

 with the result that he was pardoned, but he received no further appoint- 

 ment from the Prussian Government. In 1840 he accepted a professorship at 

 Zurich, somewhat later one at Heidelberg, and finally, in 1851, one at 

 Gottingen, where he worked until his death, in 1885. 



Under Miiller's leadership Henle worked both as an anatomist and as 

 a biologist in the invertebrate field; afterwards he also devoted himself to 

 pathology. His activities as a student of cell-life are associated with a 

 number of special essays, and also with his Allgemeine Anatomie, an excellent 

 work for its period. Among his contributions in the sphere of invertebrate 

 research his discovery of the hair-sac mites is universally known. Best of 

 all his speci/lized work, however, is his investigation of the histology of 

 the intestinal epithelium; it was he who discovered the cylindrical epithe- 

 lial cells and explained the existence of the pavement and columnar epithe- 

 lium in the various parts of the intestinal canal. He also carefully studied 

 the ciliated epithelium and its distribution and it was he who created the 

 term "epithelium." In connexion with the intestinal mucous membrane, he 

 investigated the chyle vessels with great care, particularly with reference 

 to their terminal ramifications, which had hitherto been misinterpreted. 



Henle's General Anatomy is the first histological handbook based entirely 

 upon cytology and undoubtedly the most original since the days of Bichat. 

 It begins with a chapter on animal chemistry, viewed from a contemporary 

 standpoint, and goes on to describe the part played by the cell as a primary 

 formation. His cell-theory is on the whole that of the Schleiden-Schwann 



