206 HUMAN BIOLOGY 



the architecture of the bone itself becomes changed, and the 

 trabeculae orient themselves according to the new Hnes of 

 stress. Through a more complex process, the bacterial 

 invasion of the body is opposed by substances which develop 

 within the tissues and lead to the destruction of the foreign 

 elements. It appears that any factor tending to disturb the 

 physiological equilibrium determines a reaction which 

 opposes this factor, as happens in the inorganic world, 

 according to the Le Chateher principle. Formative, regenera- 

 tive and adaptive processes bring about or maintain the 

 wholeness of the organism, as if the building-up and preser- 

 vation of this wholeness were their end. They are probably 

 the different aspects of a single principle. This principle seems 

 to group and direct in a purposeful way the processes which 

 are instrumental in producing the unity of the organism. Each 

 event is mechanically related to an antecedent event which 

 we may call its c^se. But the causal events themselves 

 appear to be linked together in a teleological manner. 

 The Aristotelian conception of efficient and final causes 

 satisfactorily expresses what seemingly happens in the 

 organism. 



It is obvious, however, that this conception does not help 

 us to understand the mechanism of the simultaneous 

 plurality and unity of the organism. The nature of the 

 purposeful processes, at which students of nature have 

 wondered for ages, has remained utterly unknown. In 

 spite of the great difiiculty of the problem, we are irresistibly 

 compelled to delve into the mystery of the constitution of 

 the body and the semblance of a driving intellect within 

 a community of tissue cells. So far, this search has been in 

 vain. But it will never cease, because human beings will 

 again and again attempt to unveil the secrets of their nature. 

 Even if the ultimate goal is never reached, such a study 

 may become of practical significance. It is well known 

 that the quality of a human being depends largely on the 

 perfection with which his component parts are coordinated. 

 If the factors that control the building-up of organs and 

 tissues during embryological development and also those 

 that determine the hereditary characteristics were discovered, 

 it would become possible artificially to improve the quality 



