366 STUDIES IN ADVANCED PHYSIOLOGY. 



One of the most vital questions is whether these living 

 cells can take some of the food out of the blood or lymph, 

 and with the oxygen from the lungs produce an oxidation 

 and so derive heat and energy for their own use. In other 

 words, do these cells manipulate the foods like the fireman 

 manipulates his coal? If so, how is the heat of such an 

 oxidation transformed into the kind of energy needed, be 

 it motion or be it chemical changes in secretion ? Or may 

 not the foods from the blood and the oxygen from the lungs 

 be built up in the living cells into living tissues, and then 

 by the burning up or chemical disintegration of this living 

 matter the energy, liberated ? To use a not very close 

 analogy, are the foods in the body burned like the coal in 

 the furnace to heat the rest of the house, or are the foods 

 like weather-boards, shingles, rafters and floors built into 

 the structure of the house, and then by partial oxidation 

 heat the house ? Does the body maintain its equilibrium 

 of temperature and derive its supply of energy out of its liv- 

 ing supply, or from the external foods? 



Of course there is no question at all as to what happens 

 to some of the foods when the body is growing. Evidently 

 they are built up into new tissues. The increase in weight 

 and size from infancy to maturity is such a magical trans- 

 lation of dead food matter into living tissue. The question 

 is here merely, are all the foods treated in this way, or may 

 a part be used merely for fuel purposes. Unfortunately 

 physiologists seem unable to agree on this point. There 

 are not lacking some who maintain, and apparently with 

 good evidence, that a large part of the food is directly oxi- 

 dized in the tissues under the influence of the living cell 

 without that food ever becoming an integral part of those 

 cells. They maintain that a proportion of the food circula- 

 ting in the blood circulates as fuel, while another part, not 

 different in kind, however, is destined to be built up into 

 tissue. They look upon the problem of nutrition as an in- 

 stance of the carpenter who uses part of his lumber to con- 

 struct his building and a second part of the lumber to burn 



