Before entering upon the study of foods it is well to consider the composition of the human body, that some idea of its chemical nature may be gained. In the United States National Museum at Washington may be found some interesting information on this subject. From there much that is contained in the following pages is taken. A complete analysis of the human body has never been made, but different organs have been examined, and chemists have weighed and analyzed portions of them, and from such data of this nature as could be obtained, estimates of the probable composition of the body have been calculated. Thirteen elements united into their compounds, of which there are more than one hundred, form it. The following table gives the average composition of a man weighing 148 pounds. Oxygen 92.4 Carbon 31.3 Hydrogen 14.6 Nitrogen 4.6 Calcium 2.8 Phosphorus 1.4 Potassium .34 Sulphur .24 Chlorin .12 Sodium .12 Magnesium .04 Iron .02 Fluorin .02 PROF. ATWATER. It will be seen from this that oxygen, carbon, hydrogen, and nitrogen constitute nearly the whole, the other elements being in very small proportions. PRINCIPAL CHEMICAL COMPOUNDS IN THE BODY The following interesting table, obtained at the National Museum, gives the principal compounds of the body. Some of the more rare organic compounds are omitted. WATER:--A compound of oxygen and hydrogen. PROTEIN { _ALBUMINOIDS_ { MYOSIN AND SYNTONIN OF MUSCLE COMPOUNDS, { or { (sometimes called "muscle { _Proteids_. { fibrin"). composed { { Albumen of blood and milk. Casein mainly of { { of milk. { { { Collagen of bone and } _Carbon_, { { tendons. } which { _Gelatinoids._ { Chondrigen of cartilage, } yield _Oxygen_, { { gristle, } gelatin. { _Hydrogen_, { { { _Hemoglobin._ { The red coloring matter of blood. _Nitrogen_. { {