THE RELATION OF CELLS TO ONE ANOTHER 207 



of human beings. Such knowledge would be still more 

 important for the future progress of medicine. Today, the 

 cure of disease depends almost entirely on the spontaneous 

 power of the organism to repair itself. The object of thera- 

 peutics is chiefly to set in motion by appropriate means 

 some of these natural mechanisms. Should we discover the 

 nature of the factors which are instrumental in the repair 

 of a diseased body, we could probably activate the cicatriza- 

 tion of wounds, the healing of fractures, and the cure of any 

 disease. For these reasons, it appears to be not only of 

 philosophical but also of practical significance to look into 

 the mechanisms that make a unity from the cell aggregates 

 composing the body of the higher animals. 



However, it should be clearly understood that for the 

 biologist the problem is purely scientific and should be 

 dealt with exclusively by the experimental method. The 

 temptation is great, in the presence of a very complex 

 problem, to build up hypotheses and to assume that they 

 are the expressions of reality. In this manner, almost every- 

 thing can be explained and, in fact, has been explained. But 

 each succeeding generation has to demolish the systems 

 created by the preceding one, and no real progress in knowl- 

 edge is made. On the contrary, if we realized that natural 

 truth can be apprehended only in fragments and by the 

 strict application of the scientific method, we would not 

 try to develop a formula disposing of the more complex 

 biological problems in a logical manner. In the course of 

 investigation, philosophy and biology should not be mixed. 

 Biology is in one realm and philosophy in another. Scientific 

 explanation and philosophic explanation, as Needham 

 said, are two distinct foods of the soul, and they are confused 

 only at great peril. Biology is full of such confusions, and 

 has suffered markedly from them. It is obvious that hypoth- 

 eses are necessary. But only hypotheses susceptible of 

 experimental verification must be constructed. We have to 

 be purely empirical. It is time to discard mere logical 

 concepts. The concepts required for the building-up of an 

 experimental science must be such that they remain true, 

 whatever future experience may be in store. Modern physi- 

 cists widely use concepts which are equivalent to a set of 



