74 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



temperature ; and when needed it will draw upon the credit of 

 the muscular and nervous systems, since one can survive with 

 a relatively small amount of either motor or mental action. 

 When, then, it may be remarked by the way, the body is not 

 properly protected in cold climates, the energy which is gener- 

 ated in the system will be dissipated in comparatively large 

 ratio in the effort to keep warm; and, as a consequence, less 

 force can be utilized in the kinds of work for which in reality 

 the organism exists ; for in the highest forms of life, whatever 

 may be true of those lower in the scale of existence, the ulti- 

 mate purposes of existence are very clearly of a mental order. 

 And in the attainment of these, motor processes are for the 

 most part essential. So that in man mental and motor activi- 

 ties are of primary importance, regarded from the point of 

 view of the raison d'etre of the organism, as well as from the 

 testimony of introspection and of the desires of the human 

 heart. 



In addition to the purposes of nutrition already indicated 

 there, should be mentioned one other. In a growing structure, 

 where continual increase in size and weight is taking place, 

 there are required nutritive substances other than those utilized 

 in carrying forward somatic and psychical functionings. There 

 are needed substances for augmenting the bulk of bone and 

 nerve and muscle, — 'materials for construction, that is to say. 

 In adult life, however, when growth has been completed, there 

 is no longer a demand for materials to build up, but only to 

 repair the wear and tear of mind and body ; so that in maturity 

 we may take account principally of the requirements of the 

 organism for the generation of force employed in the prosecution 

 of mental and motor enterprises. 



To return to our first proposition, the energy demanded to 

 sustain the activities of life must be supplied in the food stuffs 

 which are eaten. Now it is probably well known that various 

 food elements are required to meet the different needs of body 

 and brain. The nutrients best suited to furnish the materials 

 employed in making bone and muscle are not alone sufficient to 



