OF RESPIRATION. 141 



trated form of protein or nitrogenous substance : all 

 that there is containing nitrogen in bread, is the same 

 body as that which we find in meat, the only differ 

 ence being, that in bread, there is much less of it in 

 proportion to the whole bulk. It may therefore be 

 said with truth, that, in eating bread, we are in one 

 sense eating the same thing as beef or mutton. 



a. If the proportion of nitrogenous substance is 

 very small, as in the turnip or potato, the quantity 

 eaten must be greatly increased. In order to make as 

 much muscle in the body as would be added to it by 

 five or six ounces of meat, in its ordinary cooked 

 form, it would be necessary to eat at least one hundred 

 ounces of turnips or potatoes in their raw state. 

 When cooked, the proportion of water in them would 

 probably be decreased somewhat, and with the season* 

 ing employed to make them palatable, a less quantity 

 might answer. 



SECTION II. OF RESPIRATION : STARCH, SUGAR, GUM, AND 

 FAT. 



The use of starch in nutrition, has already been 

 briefly alluded to. We have seen that it is one of the 

 most abundant of all the ingredients, in most varieties 

 of vegetable food; and the question naturally arises, 

 what is the necessity, in the animal economy, for this 

 large quantity of such a substance. 



a. Starch, as was explained in one of the first 

 chapters, consists of carbon and water, or carbon 

 united with hydrogen and oxygen in the proportions 

 to form water. This is brought into the lungs by the 

 blood, after digestion, and there, or afterward in the 

 blood, undergoes what may be considered a species 

 of combustion. 



b. The carbon of the starch unites with oxygen, 

 and forms carbonic acid. This accounts for the in- 



