552 TEE POPULAR SCIENCE MONTHLY 



ogy, of Schwann and Henle in anatomy, of Du Bois-Eeymond and 

 Helmholtz in physiolog}^ and of Yirchow in pathological anatomy. It 

 is not surprising therefore that it was the proud boast of this school 

 that not only had it dispelled the vague notions of the old metaphysical 

 school and established in its stead the true scientific spirit, but that 

 it had filled so many of the chairs of medicine, physiology and anatomy 

 in the German universities that the scientific spirit has been applied to 

 " every branch of medical science, which it has in consequence drawn 

 into the circle of the exact or mechanical sciences." (Merz.) 



This is not the place to go into detail concerning the investigations 

 of Miiller and his school of physiology. His law of " specific energies," 

 Du Bois Eeymond's electro-physiology and Helmholtz's work on musical 

 acoustics and physiological optics indicate the character and scope of 

 the work. The keynote of it all Miiller himself has expressed in his 

 " Elements of Physiology " as follows : 



Though there appears to be something iu the phenomena of living beings 

 which can not be explained by ordinary mechanical, physical or chemical laws, 

 much may be explained, and we may without fear push these explanations as 

 far as we can, so long as we keep to the solid ground of observation and 

 experiment. 



These principles and the labors of this school were advanced wonder- 

 fully, in 1847, by Ludwig's invention of the kymograph and the elabo- 

 ration of methods of graphic registration, factors which established 

 this phase of physiology on a sound basis and exerted an influence which 

 medicine feels to this day. This, however, was not the only influence 

 of Miiller. As a biologist Avith general interests he stimulated general 

 biological research and it was undoubtedly this influence exerted 

 through Schwann that led the latter to grasp the importance of 

 Schleiden's work on vegetable cells and to apply the observations of the 

 latter to the cells of the animal body. 



But although the cell doctrine, in its modern conception, is the re- 

 sult of the work of these two men, Schleiden and Schwann, it is not to 

 be supposed that they were the first to study cells, for before Schleiden 

 considerable attention had been given to the structure of vegetable 

 tissues. Eobert Ilooke in 1665 had given to the spaces in cork and 

 similar structure the names of "cells"; Malpighi (1674) and Grew 

 (1683) had, as far as their low power lenses would allow, described plant 

 tissue as made up in part of cell-like cavities provided with firm walls 

 and filled with fluid, and in part of long tube-like vessels. Treviranus, 

 in 1806, demonstrated that these tubes arose as the result of cells be- 

 coming attached end to end, the intervening ends eventually disappear- 

 ing. The nucleus of the cell had been discovered in 1831 by Brown, 

 who, however, failed to realize its importance. Not so Schleiden. He 

 attached great importance to the nucleus and by the numerous observa- 



