THE NATURE AND INFLUENCE OF FOODS. 447 



At the same time it must be allowed that the body is not entirely a 

 passive agent subject to the controlling action of food, for no supply 

 could prevent the vital actions subsiding at night, or make them equal 

 both by night and day. 



There is a power inherent in the body which accepts or rejects food 

 as to amount, as well as to quality, and which might at length act 

 through the appetite, and refuse the kind supplied. Moreover, the 

 wants of the body vary from many other well-known influences, and 

 cause an increase or decrease in the vital actions which proceeds pari 

 passu with the consumption of the transformed or stored-up food in a 

 degree proportionate to the cause, but such effects are often more rapid 

 and transitory than that of food. 



The variations in the requirement for food are induced by age, 

 climate, season, and degree of exertion, and will be more fully dis- 

 cussed in the work on Dietaries ; but it may now be desirable to give 

 a glance at some of them. 



In reference to age, there can be no doubt that all vital processes, 

 including the action of foods, are greater and more rapid in early, and 

 less and slower in later, than in mature life, and in both the former a 

 more frequent administration of food is necessary. In early life, more- 

 over, there is the important function of growth, which demands a large 

 and more frequent supply of food, not only for daily wants, but to 

 promote a due increase in the bulk of the structures of the body. I 

 have also shown that the season of the year has also a decided influ- 

 ence over the vital actions, so that they are the greatest in the spring 

 and the least at the end of summer. 



The action of climate is similar to that of season, and shows that 

 the vital actions are greater in cold than in hot climates, and in the 

 uplands than in close valleys. 



The influence of exertion over vital changes is immediate and pro- 

 portionate, while the subsidence with the rest is less rapid than the in- 

 crease. The following table of experiments upon myself shows the 

 proportionate effect of exertion of varying degrees on the basis of the 

 increased volume of air inspired : 



No. 6. 



The lying posture being 1 



The sitting posture is 1.18 



Reading aloud or singing " 1.26 



The standing posture " 1-33 



Railway travelling in the 1st class "1.40 



" " " 2d class "1.5 



" " upon the engine, at 20 to 30 miles per hour . " 1.52 



" " " " 50 to 60 " " " 1-55 



" " in the 3d class " 1.68 



" " upon the engine, average of all speeds . " 1.58 



" " " " at 40 to 50 miles per hour . " 1.61 



m 30 to 40 " " " 1.64 



