g8 THE SPIRIT OF THE SOIL 



Some men, as they do still, took refuge in con- 

 ceptions of vitalism, shelving in fact the problem as 

 insoluble; others are pressing on in search of fresh 

 material evidence to illuminate what remains 

 obscure. It may well be that the problem of the 

 living organism will never be solved by the physiolo- 

 gist, for as the research proceeds fresh factors are 

 continually bringing themselves into evidence, and 

 with the increase of knowledge it becomes more and 

 more possible to form some appreciation of the 

 extent of the unknown. 



It was through researches undertaken on disease 

 that the physiologist was brought to recognize the 

 existence and importance of accessory food sub- 

 stances. Both experiment and observation had 

 long ago accustomed him to the idea that minute 

 quantities of substance might have astonishingly 

 important results on the welfare of the body. 

 Cretinism, with all the disarrangement of growth 

 and function associated with it, had been proved to 

 be conditioned by the absence of the excretions of 

 the thyroid gland. Starling and others had been 

 pressing their researches to elucidate the elaborate 

 chemical mechanism by which the conduct of the 

 body tissues is regulated, and the blood had come 

 to be regarded no longer as a simple liquid in which 

 red and white blood corpuscles floated about their 

 business, but as an intensely complex aggregate of 

 chemical substances, some of which were necessary 

 for the hourly needs of the body, while others were 

 present there on the bare chance of the emergency 

 arising that they were designed to meet. 



