378 LUDWIG AND MODERN PHYSIOLOGY. 



mental results being of so unequivocal a kind that, even had they not 

 been continued, they must have been received without hesitation. How 

 is such a case as this to be met? The " Neovitalists " answer promptly 

 by reminding us that there are cells, i. e., living individuals, placed at 

 the inlets of the system of drainage without which it would not work, 

 that these let in less or more liquid according to circumstances, and 

 that in doing so they act in obedience, not to physical laws, but to vital 

 oues — to internal laws which are special to themselves. 



Now, it is perfectly true that living cells, like working bees, are both 

 the architects of the hive and the sources of its activity, but if we ask 

 how honey is made it is no answer to say that the bees make it. We 

 do not require to be told that cells have to do with the making of lymph 

 as with every process in the animal organism, but what we want to 

 know is how they work, and to this we shall never get an answer so long 

 as we content ourselves with merely explaining one unknown thing by 

 another. The action of cells must be explained, if at all, by the same 

 method of comparison with physical or chemical analogues that we 

 employ in the investigation of organs. 



Since 1890 the problem of lymph formation has been attacked by a 

 number of able workers, among others here in London, by Dr. Starling, 

 of Guy's Hospital, who, by sedulously studying the conditions under 

 which the discrepancies between the actual and the expected have 

 arisen, has succeeded in untying several knots. In reference to the 

 whole subject, it is to be noticed that the process by which difficulties 

 are brought into view is the same as that by which they are eliminated. 

 It is one and the same method throughout, by which, step by step, 

 knowledge perfects itself — at one time by discovering errors, at another 

 by correcting them ; and if at certain stages in this progress difficulties 

 seem insuperable we can gain nothing by calling in even provisionally 

 the aid of any sort of eidolon, whether "cell," " protoplasm," or inter- 

 nal principle. 



It thus appears to be doubtful whether any of the biological writers 

 who have recently professed vitalistic tendencies are in reality vitalists. 

 The only, exception that I know is to be found in the writings of a well- 

 known morphologist, Dr. Hans Driesch, 1 who has been led by his 

 researches on what is now called the mechanics of evolution to revert 

 to the fundamental conception of vitalism that the laws which govern 

 vital processes are not physical, but biological — that is, peculiar to the 

 living organism and limited thereto in their operation. Dr. Driesch's 

 researches as to the modifications which can be produced by mechanical 

 interference in the early stages of the process of ontogenesis have 

 enforced upon him considerations which he evidently regards as new, 

 though they are familiar enough to physiologists. He recognizes that 



driesch. Entwicklungsmechanische Studien. A series of ten papers, of which 

 the first six appeared in the Zeitsch. f. w. Zoologie, Vols. LIII and LV; the rest in 

 the Mittheilungen of the Naples Station. 



