vi 



the fifties, in order to appreciate its extraordinary influence, for it 

 was in 1852 that the first volume appeared. To those whose concep- 

 tions were derived from the current teaching of that time, it seemed 

 destructive. It made no mention of " vital forces ; " it did not even 

 give a definition of life or of organisation, but defined physiology as 

 " the determination of the activities (Leistungen) of the living body, 

 with reference to the elementary conditions on which they are 

 dependent;" the writer's aim being to resolve these conditions into 

 their simplest elements, and so bring them within the scope of 

 chemical and physical laws. Accordingly, he began his treatise with 

 the discussion of the elementary endowments of the structure or 

 framework of the living body, and of the processes in which these 

 endowments manifest themselves ; seeking to arrive at a clear con- 

 ception of each vital function by regarding it as a complex of 

 constituent processes severally definable in chemical or physical 

 terms. The book set forth no " biological principles," and therefore 

 had no interest for the general reader. It was for students and for 

 students only, but for them it was a revelation, a forecasting of the 

 physiology of the future for those who were about to make it. The 

 second edition was published in 1862, but had no successor. 



It may be noted here that Ludwig, like Darwin, avoided contro- 

 versy. When, in 1875, certain important investigations which had 

 been conducted in the Leipzig laboratory were made the subject of 

 inconsiderate criticism, he persistently resisted the importunity of 

 friends, who pressed him to reply, saying that he preferred to leave 

 the future to judge between him and his distinguished opponent. 



In the preceding pages I have endeavoured to give the reader an 

 idea of the chief directions which Ludwig's activity followed. No one 

 who is acquainted with the modern development of the science of 

 physiology can fail to see that the history of Ludwig's life work was 

 in truth that of the science which he did so much to create ; for its 

 development from small beginnings during the second half of the 

 century has coincided in a remarkable way with his career as a dis- 

 coverer. In certain lines of investigation, as, for instance, those which 

 relate to the localisation of the higher functions of the nervous 

 system, Ludwig took lift J e part, but in every other direction his 

 researches have been of fundamental importance. All the great 

 functions of the organism, whether mechanical or chemical, have 

 been investigated by him collectively and separately — as processes by 

 themselves, in their relation to the whole organism, and as regulated 

 by the nervous system- 



That one man, however endowed, should have been able even in so 

 long a period of activity to accomplish so great a work can only be 

 explained by referring to the conditions of the earlier years of his 

 academical life. At Marburg he was engaged in two lines of work 



