— 6 — 



that nearly all foods, no matter of what description, contain a sufficient 

 amount of these sub^tances, which comprise, mainly, lime, potash, and 

 phosphoric acid, with varying quantities of sodium, iron, magnesia, sul- 

 phuric acid, hj'drochloric acid, silica, etc. 



Nitrogenotis, or Proteids. — The nitrogenous matters of the body, of which 

 the major part are called proteids, the only ones that contain nitrogen, 

 are found mostly in the niuscle, gelatinous part of the bones and tendons, 

 brain, nerves, and internal organs; in short, all the working machinery 

 of the body is composed principally of this important material. Simi- 

 larly, in the foods, almost the entire nitrogenous part is called protein, 

 signifying, by its Greek derivation, to take tirst place, ^\'e receive the 

 protein from the white of egg, the myosin of lean meat, casein of milk, 

 gluten of wheat, gelatinous parts of bones, tendons, etc. 



The necessity of this constituent in the daily diet depends not only 

 upon its important relation to such tissues as muscle, blood, nerves, 

 tendons, etc., but also upon the fact that as far as we know no albu- 

 minoid or protein matter is formed in the body, except by the trans- 

 formation of similar substances presented to it from external sources. It 

 cannot be obtained by the conversion of any other material. 



The protein can be changed into fats, and thus may serve as fuel for 

 the body, hutfats cannot replace protein. 



Non-nitrogenous, or Carbohydrates arid Fats. — The non-nitrogeneous 

 portions of the solid constituents of the body are principally fat — the 

 material which is consumed in the production of heat and energy. The 

 source of this substance in foodstuffs is comprised in all those portions 

 which are free from nitrogen. They are divided into two main classes — 

 the carbohydrates and fats — and are identical with those found in the 

 body, with the exception of starch and sugar, which aro not found as 

 such in any large amount in the healthy body. 



The carbohydrates comprise starch, sugars, gums, and woody fiber; 

 the latter, in the statement of analyses of foods, is reported separately, 

 while the remainder of the aliove are, in order to conform to the general 

 usage, chissed together under tlie head of " nitrogen-free extract." The 

 gums play only a secondary part as regards the nutritive value of the 

 food. The carl)ohydratcs are mostly changed into fats and then used as 

 fuel; althougli it must be remembered that, for the purpose of heat, fat 

 is worth 2.25 times as much as carl)ohydrates, that is, 1 pound of fat is 

 equivalent, when used as fuel, to 2.25 pounds of starch, sugar, etc. ^\'llen 

 there is a deficiency of these Clements in tlic UhmI, tlic fat of tlic body is 

 drawn upon. 



The fat, as might be supposed, varies morc tlian any otlu-r substance 

 of the body, its accumulation being reguhited l)y diet, niuscular 

 exercise, etc. Sh'c]), as well as inactivity, favors the storagc of fat, Mliich 

 in the average body constitutcs 20 \)vv ccnt of the total weight. 



If the food-supply is cut off, the surplus fat storcd U}> in the Itody is 

 drawn upon to keep the macliinery going, and if this continues a oor- 

 r(S]»onding amount of ])rotein is eonvert(>d into fat and used as such. 

 Tlius we See tliat Ity having a ])roper })roi)orlion of fat in our food we 

 protect not only the fat of the liody, but indirectly, and iiiost iiuiioitant, 

 the protein of tlic muscle and blood. We receive our fat from such 

 foods as the butter of milk, fat of nu-aj, oil of seeds and fruits such as 



