64 APPLIED PHYSIOLOGY 



' It is important to bear in mind, however, that this 

 inadequate production of heat does not always translate 

 itself by the expression of "chilliness"; the effect of cold 

 is often totally unlike that of a chilly sensation. It 

 produces a vague uneasiness, a feeling of depression, 

 resulting from the lowering of the organic activity, and 

 many periodic forms of disease are probably connected 

 therewith. Without ^positively " feeling cold," the person 

 so affected need only enter a well- warmed apartment to 

 be at once aware of a rein vigor ated condition.' 



The immediate effect of a warm meal in raising the 

 temperature of the body is more apparent than real, 

 being due to stimulation of the circulation, with conse- 

 quent better distribution of the blood in the periphery. 

 Apart from this effect, however, food is undoubtedly an 

 important source of heat after it has had time to be 

 digested and absorbed. Of the chemical constituents of 

 the food, protein is the most rapid developer of heat, 

 probably owing to its speedy cleavage and the partial 

 oxidation of the nitrogenous part of its molecule already 

 referred to. Next to it in potency is carbohydrate, 

 whilst fat comes lowest in heating power.* These facts 

 have important bearings on the dietary suitable for hot 

 weather and warm climates. 



THE NERVE MECHANISM OF TEMPERATURE EEGULATION. 



Variations in heat loss from the surface of the body 

 are brought about through the medium of the vasomotor 

 and sweat-secreting nerves. The mechanism involved 



* If the heat-generating power of protein be taken as 20, that of 

 carbohydrate is 10, and that of fat 7. 



