398 THE HISTORY OF BIOLOGY 



school, which has previously been mentioned: the nucleus formed through 

 an accumulation of a granulate substance, the cell formed round the nucleus 

 and consisting of membrane, nucleus, and fluid content. Cell-division is 

 denied as far as the animal kingdom is concerned; the cell-formation is 

 rather compared with the emulsive phenomena that arise when oil and al- 

 bumen are shaken together — an attempt at an explanation which, as is 

 well known, has been the subject of endless variations in modern time. On 

 the other hand, Schwann's comparisons between cell-formation and crys- 

 tallization are not accepted. Henle adopts a decidedly critical attitude in 

 regard to speculations on the primary vital phenomena. "Explaining a 

 physiological fact means tracing its necessity from physical and chemical 

 natural laws. It is true, even these laws offer no explanation as to the ulti- 

 mate grounds, but they make it possible to combine a mass of details under 

 one point of view." On the life -force theory adopted universally by his con- 

 temporaries he passes the following striking judgment: "The life-force is 

 formally as good an explanation as the force of gravity, but it is one force 

 the more and this is at variance with our striving after unity." 



Henle thereupon proceeds to give an account of the tissues, and, of 

 these, first of all the epithelial system, which indeed was best mastered 

 and is very well expounded. A number of other details are also excellently 

 explained, especially the vascular musculature, which is here for the first 

 time satisfactorily dealt with. In regard to the division of tissues, Henle is, 

 of course, far in advance of Bichat, but even his system is, from the modern 

 point of view, difficult of comprehension; in particular, the category nowa- 

 days called connective tissue is split up into a mass of sub-headings which are 

 often somewhat unhappily formulated. Another weak chapter is that on 

 the glandular system, as indeed Henle himself admits, referring to the 

 paucity of the investigations that have been made in that sphere. But, on 

 the whole, Henle's general anatomy deserves the judgment passed on it by 

 a later histologist who declared that it laid the foundation of modern his- 

 tology and on that account will survive. 



Karl Bogislaus Reichert was born in 181 1 in a provincial town in East 

 Prussia, where his father was mayor. He studied at Konigsberg under von 

 Baer and in Berlin under Miiller, was called to a professorial chair first at 

 Dorpat, then at Breslau, and finally in Berlin, where after Miiller's death, 

 when the latter's professorship was divided, he took over the professorship 

 of anatomy, which he retained until his death, in 1883. He began his activi- 

 ties as a comparative anatomist with a valuable work on the development of 

 the gill-arches in the Vertebrata and another equally eminent work on the 

 embryonic formation of the frog's head. He then devoted himself to cytology 

 in the spirit of Schwann and applied the latter's theories to the evolution of 

 frog's spawn, not, it is true, without falling into the misconception prevalent 



