THIRTEENTH ANNUAL MEETING. 175 
or all of certain classes of compounds charcterized by contain- 
ing carbon, oxygen, hydrogen, and with them, nitrogen. The 
most important are the proteids or albuminoids, of which albu- 
men, the white of egg, fibrin of blood, casein of milk, myosin, 
the basis of muscle, and gluten of wheat, are examples. Allied 
to these, but occurring in smaller proportions in animal tissues 
and foods, are the nitrogenous compounds that make the basis 
of connective and other tissues. Gelatin is derived from some 
of these tissues, and may be taken as a type of the compound 
of this class. As these constituents are of similar constitution 
and have similar or nearly similar uses in nutrition, it is cus- 
tomary to group them together as protein.* What we should 
especially bear in mind, then, is that protein is a term applied 
to the nitrogenous constituents of our foods, and we shall see 
these are, in general, the most important, as they are most cost- 
ly, of the nutrients. 
Fats.—We have familiar examples of these in the fat of meat, 
(tallow, lard,) in the fat of milk which makes butter, and in 
olive, cotton seed, and other animal and vegetable oils. The 
fats consist of carbon oxygen and hydrogen and contain no ni- 
trogen. In nutritive value, as in cost, they rank next to the 
protein compounds. For some of the nutritive functions, in- 
deed, the fats equal or exceed protein in importance. 
Carbo-hydrates—Starch, cellulose, (woody fiber) sugar, and ino- 
osite, (“ Muscle sugar’”’) and other similar substances are called 
carbo-hydrates. Like the fats, they consist of carbon, oxygen 
and hydrogen, but they have less carbon and hydrogen, and 
more oxygen than the fats. 
Mineral matters or Ash—When vegetable or animal matters 
are burned, more or less incombustible material remains as ash. 
The ingredients which make the ash are called mineral matters, 
or sometimes, salts. They are for the most part compounds of 
the elements, potassium, sodium, calcium and iron with chlorine, 
sulphuric acid and phosperic acid. Sodium combined with chlor- 
ee EE eee 
* The muscular tissues of animals, and hence the lean portions of meat, fish, etc., contain 
small qualities of so-called nitrogenous extractives—creatin, carnin, etc., contained in extract 
of meat, etc., which contribute materially to the flavor, and somewhat to the nutritive ef- 
fect of the foods containing them. They are not usually deemed of sufficient importance, 
however, to be grouped as a distinct class in tabular statements of the composition of foods. 
