THE RELATIONS OF THERAPEUTICS 159 



chemical laws, but that other conditions not present in test-tube 

 experiments also play a part. 



Here we must turn for a new mode of thought to Schwann's 

 magnificent discovery of the animal cell. Through it the anatomical 

 conception of the organism was placed upon an entirely different 

 basis. As human tissues consist of cells, and the entire development 

 of man results through cell activity, this must naturally lead us to 

 assume that the purely chemical part of human existence takes 

 place in as many cells as the individual possesses. That which in 

 chemistry we describe as a reaction must, if we leave out of the ques- 

 tion the chemical processes in the digestive tract, take place in small 

 separate spaces, such as the chemist never employs for his experi- 

 ments. The chemist does not usually assume that reactions occurring 

 in such exceedingly restricted spaces differ from those which take 

 place in the vessels used for his operations. It will be the task of the 

 biologist to investigate whether this chemical action in the cells 

 undergoes any modification through limitation of space. 



I have been able to prove in the course of investigations on the 

 "dead space in chemical reactions outside the organism" that power- 

 ful phenomena of friction take place here. This could not be de- 

 finitely proven experimentally in the case of all reactions, but some- 

 times it could be shown that if the space inclosing the fluid be 

 diminished, the reactions in comparison with those which occur in 

 larger spaces are retarded if not completely arrested. The objection 

 might be raised that in these experiments the retardation or arrest 

 of reaction was generally due to the nearness of solid walls, but it 

 was observed that the same phenomenon is noticed when the bound- 

 ary of the fluid is only formed by surface tension, for the tense 

 surface behaves like a firm elastic membrane toward the fluid, as is 

 the case with many cells. The results showed that whenever the 

 friction of the liquid increased, the chemical reaction was retarded. 

 This hindrance of the reaction in small spaces, which differs in the 

 case of different reactions, naturally permits the conclusion that, 

 contrary to what happens in large spaces, in small ones entirely 

 different reactions will result. Of course, this observation can only 

 serve as the initial proof that the chemical action in the cells is unlike 

 that w r hich occurs in test-tube experiments. We see that here also 

 the argument for the acceptance of the theory of vital energy which 

 I pointed out to you as possible, is refuted. 



As regards drugs and their absorption these chemical processes 

 probably play an important part, for we observe that reactions 

 occurring outside of the organisms do not take place within it, and 

 on the other hand, combinations arise which are difficult to produce 

 externally. Here we may mention, by way of illustration, the facility 

 of decomposition of common salt into hydrochloric acid and alkali. 



