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SCIENCE 



[N. S. Vol. XLIV. No. 1133 



In the newest physiology there is noticeable an 

 undercurrent which offers as its conception with 

 always less reservation that not even the simplest 

 life processes, as for example respiratory gas ex- 

 change and lymph formation, can be explained 

 wholly on a physico-chemical basis, but that they 

 chiefly depend on vital processes in the cells. . . . 

 But this new vitalism distinguishes itself in a 

 very important point from the old. It does not 

 assume the existence of a peculiar, mystic vital 

 force, and does not break away from the funda- 

 mental view, which the last fifty years have made 

 the unalterable possession of physiology, with the 

 truth that the principle of the conservation of 

 energy applies to living as well as to dead nature. 

 This being so, it is of relatively secondary im- 

 portance whether the complicated processes, which 

 take place in living beings, can or can not be ex- 

 plained by the physics and chemistry of our time. 

 In any case they follow definite laws, and are not 

 called out by a whimsical power, which can at the 

 one instant be indefinitely strong and at the next 

 nul. So if we say that this or that process is at- 

 tributable to cell activity, that signifies nothing 

 else than that our present physical and chemical 

 knowledge is still insufficient to completely ex- 

 plain these processes, and that the right explana- 

 tion will possibly only be found if the forces work- 

 ing within the cell lie more clearly in the sight of 

 the experimenter. 



And if it were true that many theories which 

 Ludwig expressed had lost some of the likelihood 

 which they formerly seemed to have, what has that 

 to do with their importance for our science? In 

 all natural science we meet the observation that 

 theories have only a limited life, that one theory 

 after a shorter or a longer time must give place 

 to another, which can indicate more completely or 

 better than its predecessor the character of the 

 phenomena which it should explain. A theory is 

 then good, and has an importance in the develop- 

 ment of science, if it is of such a kind that it 

 leads to new investigations, based on direct ob- 

 servation of nature, through which science wins 

 in breadth and depth. If through it such facts 

 shall be discovered as are not in harmony with 

 the theory, which they have, nevertheless, to thank 

 for their discovery, then the theory falls. But it 

 falls with honor, for it has led to the discovery of 

 new truths, and has constructed an important link 

 in the development of science. Whatever the fate 

 of Ludwig 's theoretical views, we can surely say 

 that they have greatly enriched science, and so 

 bear the stamp that is the sign of good theories. 



It is interesting to read the estimation of 

 Ludwig 's character and his methods of 

 work by another great investigator, Wil- 

 helm His, the great Leipzig anatomist : 



Ludwig 's weapons of research were an uncom- 

 mon sharpness of analysis of living processes 

 under observation, an always clear formulation of 

 the question, and an absolute reliability of the 

 method of attack. It was of great importance for 

 his career that he was a schooled anatomist and 

 controlled microscopical technique to a remarkable 

 degree. From his anatomical knowledge came his 

 consummate and careful technique as an experi- 

 menter on living animals, in which only Magendie 

 and Claude Bernard are to be compared with him. 

 Moreover, he had at his command a shrewd intui- 

 tion, without which the clearest thinker is often 

 powerless in the investigation of living processes. 

 Nature does not always allow herself to be con- 

 quered by logic, her ways are frequently hidden, 

 and she reveals herself only to him who has sharp- 

 ened his sight for insignificant traces, by persistent, 

 faithful observation. Ludwig had to a high degree 

 a love for personal observation, and a successful 

 preparation or a striking experiment was for him 

 an esthetic pleasure. He placed direct perception, 

 in the study of living nature, far above working 

 with abstract conceptions. 



As has been said, when Ludwig was ap- 

 pointed to the chair of physiology in Leip- 

 zig his first task was the planning of a 

 physiological institute. This institute was 

 the seat of Ludwig 's labors for nearly 

 thirty years; it saw the development of 

 many of the greatest physiologists of the 

 past five decades; it was the birthplace of 

 discoveries which have been of inestimable 

 value to medical thought; and the remark- 

 able success of the ideals and methods 

 which he, as director, put into practise, 

 caused it to become the model for many 

 others. The plan is a witness of his breadth 

 of view, and the recognition that the prob- 

 lems of physiology can be solved only 

 through a knowledge of the structure of 

 the parts involved, and a study of both the 

 physical and chemical changes occurring 

 within them, and that under ideal condi- 

 tions, all of these forms of work should go 



