CARL LUDWIG AND CARL THIERSCH. 341 



on the circulation of the blood, and, lastly, the exhaustive work on 

 respiration by Regnauld and Reiset. Among Ludwig's personal 

 friends, E. Du Bois-Reymond had between 1840 and 1850 con- 

 structed a theory of molecular physics of the nerve and muscle tissue, 

 and Helmholtz, by means of wonderfully ingenious methods, had 

 measured the rate of transmission of the stimulus in living nerves. 



The road for physical investigations in physiology was, therefore, 

 already open when Ludwig's book appeared. Moreover, the idea of 

 a vital force, which on account of its obscurity had excited so much 

 opposition, had now become meaningless for scientific investigation, 

 and had besides received its deathblow through Lotze in 1842. 

 What, however, was totally lacking before the appearance of Lud- 

 wig's book was a thorough introduction of physical reasoning and 

 methods in physiological instruction. Anatomy was still the ruling 

 branch of science even in physiology, and in some chapters of the 

 latter the physiological problems were actually left out in favor of 

 anatomical or comparative anatomical explanations. This was the 

 more natural, because physiology was still taught by anatomists in 

 most of the universities. Moreover, the regular course of instruc- 

 tion afforded the young physician abundant opportunity of acquiring 

 a thorough anatomical education, while on the other hand a more 

 rigorous training in physics was extremely difficult to obtain. Even 

 to the present day this difficulty has never been satisfactorily over- 

 come. 



As anatomical demonstrator and professor, Ludwig himself had 

 been through the dissecting room; he was all his life an excellent 

 anatomist, and thought exceptionally highly of the mission of anat- 

 omy. However, in many ways his ideas of this mission differed 

 from those of his predecessors, and even his language was often 

 unlike what had hitherto been in use. He was especially energetic 

 in opposing the idea that the mere description of forms could lead the 

 way to a true understanding of physiology. The controversies be- 

 tween Ludwig and his opponents were vigorously carried on for 

 several years, but at last they grew to understand one another better, 

 and anatomists now have for years been accustomed to respect Lud- 

 wig as a valuable fellow- worker and one of the most eminent pro- 

 moters of their science. 



Perhaps nothing is more significant of Ludwig's point of view at 

 the time of his first appearance than the arrangement of matter 

 in his work on physiology. Ludwig's great predecessor, Johann 

 Miiller, had prefaced his manual of Physiology with a general chap- 

 ter on organic matter, on organisms and life, and then proceeded to 

 a description of the great vital functions: the formation and circula- 

 tion of the blood, respiration, nutrition, etc. Ludwig, on the other 



