ON THE NATURE OF LIFE 213 



because its knowledge is incomplete and its concepts are not yet 

 formulated. This latter conclusion is, however, all that we seek to 

 make here biology, not having attained the concepts that will 

 enable it successfully to predict, has not yet been " explained." 



Now let the reader refer back to our discussions of Chapter VIII. 

 It is very clear that organic behaviour (in the cases of the higher 

 animals, at all events) is indeterminate: it cannot be predicted. 

 When anyone says that physical determinism must hold in organic 

 as well as in inorganic functioning, he means that it ought to 

 hold because the concepts by means of which we " explain " life 

 ought to be the same as those by which we explain inorganic 

 happening. It may be that they are the same, and that by-and- 

 by biological predictions will be successful; but the plain fact is 

 that, so far as we know, much of the behaviour of the higher 

 animal is spontaneous, and cannot be predicted, while no satis- 

 factory logical proof can be given of determinism in its application 

 to organic acting. 



We are not going to argue here that, because physiological 

 investigation discloses no activities in the animal body other than 

 physical and chemical ones, organic happening is necessarily the 

 same thing as inorganic happening. It is quite true that the 

 physiologist finds nothing in the functioning of an organ but 

 physical and chemical reactions, for, because of his methods, these 

 are all that he could possibly expect to find. When he studies the 

 submaxillary gland, say, he finds that a saliva, a liquid of a 

 certain chemical composition, is secreted and poured into the 

 mouth. He finds that this secretion occurs when food has 

 entered the mouth, and when the nerve endings there have been 

 stimulated chemically by the substances of the foodstuff. A 

 reflex occurs and the gland functions. The nature and abund- 

 ance of the saliva depend on various factors blood-pressure, 

 osmosis, hydrostatic pressure, chemical reactions in the cells, 

 etc. and investigation has taught us very much as to the ways 

 in which these various factors act. We have dealt in some detail 

 with this typical example of animal activity in the Appendix, 

 and we may leave the reader to study it further in the textbooks. 

 He will see, however, that all that has been obtained by in- 

 vestigation is a description of the manner of functioning of the 

 gland; there are nervous impulses, changes in the calibre of the 

 bloodvessels, changes in the pressure of the circulating blood, 

 changes in the pressure of the salivary liquid contained in the duct 



