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excites violent muscular twitchings ; the same stimulus applied to the posterior roots is 

 attended with no such effect. . . . If in the same frog the three posterior roots of the 

 nerves going to the hinder extremities be divided on the left side, and the three anterior 

 roots on the right side, the left extremity will be deprived of sensation, the right of 

 motion." {Physiology, pp. 692-694.) 



He had a clear conception of reflex action, studied the problems of 

 consensual movement and excentric sensation, formulated the law of 

 " specific energies " for the sense organs, made fundamental observa- 

 tions on the production of voice, and conduction of sound in the 

 tympanum. 



With Purkinje he was amongst the first to apply the microscope 

 to the study of animal tissues, and helped his pupils to build up 

 modern histology. He recognised the resemblance between the cells 

 of the chorda dorsalis and those of plants. He gave careful descrip- 

 tions of the structure of cartilage cells, recognising their nucleus, and 

 was the first to prepare chondrin. He grouped the cellular tissues 

 with others to form the " Bindegewebe " or connective tissues. He 

 made experiments on blood coagulation, resuscitated the experiments 

 and observations of Wm. Hewson, and helped Schwann to his 

 discoveries on digestion. 



His work, Elements of Physiology, so far as it goes, is still 

 unsurpassed, and contains a mine of information. At the suggestion 

 of Dr. George Burrows, it was translated by Dr. Wm. Baly, 1st ed., 

 1837, 2nded., 1840. 



As showing the titanic might of his genius and industry, in 

 twenty-five years he published over two hundred papers, besides 

 doing all his other work. Amongst his pupils may be mentioned 

 Schwann, Henle, Briicke, Du Bois-Reymond, Virchow, Helmholtz, 

 Claparede, Reichert, Lieberkiihn, R. Remak, &c. 



THEODOR SCHWANN. 



1810-1882. 



ALTHOUGH Schwann spent the greater part of his life in 

 Belgium, his work was done in Berlin, when Johannes Miiller 

 was Professor and J. Henle Prosector. The fifth child 

 amongst thirteen, Schwann was born at Neuss near Dusseldorff'. 

 Cologne is associated with his early days, when he attended the 

 College of the Jesuits ; and in Cologne he died. The religious, the 

 theological factor, was a powerful and dominant one in Schwann. He 

 entered the University of Bonn in 1829, where he had the good fortune 

 to become a pupil of Johannes Miiller. " This event fixed his 

 destiny." He determined to study medicine. While there he witnessed 

 Midler's experiments on the spinal nerve roots of the frog. After 



