knowledge of nut culture, we may look for a much larger use of nuts as "meat substitutes "1 in the future. Even at present prices the economy of nuts both as sources of energy and of protein will doubtless be surprising to many who have not previously compared the composition and cost of typical articles of these groups.

Typical nuts resemble typical meats, not only in their richness in protein but also in their lack of a satisfactorily balanced mineral and vitamin content, being poor in calcium and in vitamins A and C. They may be regarded as substitutes for other seed products, or for meat, but not as a satisfactory substitute for dairy products or eggs.

In the work of Johns, Finks, and Gersdorff, coconut protein was found by feeding experiments to furnish all the essential amino acids. Since the chemical examination shows it to be fairly high in lysine it should be of value as a supplement to the grain proteins. Its lysine content of about six per cent gives it rank in this respect somewhat below the milk proteins and about equal with the proteins of eggs, meat, fish, and gelatin.

Cajori has shown that nuts furnish proteins which are adequate for growth and that they are good sources of vitamin B. Working with rats which consumed about 6 to 8 grams of total food per day, he found that if almonds, English walnut, black walnut, chestnut, Brazil nut, or pecan was included in the ration to the extent of 1 to 2 grams per day, the nut sufficed as sole source of the B vitamin. This would imply that nuts are nearly but not quite as rich in vitamin B as are the whole cereals, the dry legumes, or the solids of milk or eggs.

While, broadly considered, the nuts are similar in nutritional character to the grains, in respect to protein they may supplement the proteins of certain grain products. Eddy and Eck

1 To speak of nuts as "meat substitute is natural under present conditions and reflects the prominence which has been given to meat and the casual way in which nuts have been regarded for some generations. Looking at the matter in evolutionary perspective it might be more logical to speak of meats as "nut substitute" instead.

man comparing peanut protein with meat protein in this respect conclude:

"When the protein supplementing power of peanut flour is compared with that of muscle protein by feeding rations so constituted as to contain only about 10 per cent of protein, 6 to 7 per cent of this protein being contributed by wheat flour and the rest by peanut flour or meat residue, respectively, and when these rations are further supplemented with 3 per cent of butterfat, 4 per cent salts and brought to nearly equal caloric value per gram; the peanut flour proves slightly superior to the meat as a growth producer and markedly superior for promoting reproduction."

Johns and Finks had found that bread made with a mixture of 25 per cent peanut flour and 75 per cent wheat flour (74 per cent extraction) furnished adequate proteins and water-soluble vitamin for normal growth.

Johns reports the quantitative digestibility of the peanut to be good. Fed in the form of peanut flour it showed digestibility coefficients of protein 89 per cent, fat 96 per cent, carbohydrates 97 per cent. He recommends the use of bread containing 25 per cent of peanut flour.

Since the ravages of the boll-weevil made it unprofitable to grow cotton in many parts of the South, increased attention has been given to peanut culture, and a number of mills which formerly produced cottonseed oil are now pressing oil from peanuts. The residual "peanut press cake" is rich in protein, and the work of Johns and Jones of the Bureau of Chemistry, United States Department of Agriculture, has shown that peanut proteins are relatively rich in basic amino acids in which the cereal proteins are relatively poor, and promise therefore to be of considerable value for feeding in connection with grain products. In 1916, they described two globulins from the peanut, arachin and conarachin, containing 4.96 and 6.55 per cent of basic nitrogen, the latter figure being characterized as the highest which

had been reported for any seed protein. For comparison they give the figures shown in Table 55.

TABLE 55. BASIC NITROGEN IN PERCENTAGE OF THE TOTAL NITROGEN OF

Shiba and Koyama found peanut protein somewhat more efficient than soy bean protein in the support of growth.

Morgan and Heinz have shown that the protein mixture contained in the almond functions efficiently in human nutrition. Rose and MacLeod (working with grown people) found that the calcium of almonds was fairly well utilized but in most cases not as well as was the calcium of milk.

The Place of Fruits and Vegetables in the Diet

Considered as sources of energy, potatoes and dry beans and peas are at ordinary prices about as economical as grain products and much more economical than the meats; while the dried fruits are comparable in economy as fuel with milk, butter, and the fatter and cheaper kinds of meat. Even those fruits and

1 The term "basic nitrogen" covers the nitrogen present in the protein in the form of the radicles of those amino acids which are basic (more basic than acidic) in their chemical nature. Arginine, histidine, and lysine belong to this group of amino acids.

green vegetables which are eaten for flavor with little thought of food value, and which are often thought of as luxuries because of their high water content, will often be found to furnish energy at no greater cost than many of the familiar cuts of meat when account is taken of the extent to which the fat of the meat is usually lost or rejected in cooking or at the table.

That the dry legumes are both absolutely and relatively rich in protein is a fact so well recognized as not to require elaboration here. Less generally realized is the fact that while the green vegetables contain too much water to show high absolute values or percentages by weight of protein, yet they show as much or more of the total fuel value in the form of protein as is customary or desirable in ordinary dietaries. In fruits, on the other hand, the relative proportion as well as the absolute amount of protein is usually low. The proportion of energy furnished by protein, as well as other data, may be found for all the common articles of food in the table of 100-Calorie portions at the back of this book (Appendix D).

The vegetables differ among themselves in the nutritive efficiency of their proteins. Probably the proteins of the leaf vegetables are, weight for weight, of somewhat higher nutritive efficiency than the proteins of the seeds. Even among the latter, there are also differences, which naturally have been studied mainly in the legumes, since these are so generally regarded as significant largely if not chiefly for their protein content. Finks, Jones, and Johns, in their paper "The Rôle of Cystine in the Dietary Properties of the Proteins of the Cowpea, Vigna sinensis, and of the Field Pea, Pisum sativum" (Journal of Biological Chemistry, Vol. 52, pages 403-410) have pointed out that the proteins of the cowpea, Vigna sinensis, like those of the beans of the genus Phaseolus, are limited in their nutritive value by a low content of cystine, while the proteins of field peas, Pisum sativum, fed at the same level, were adequate for growth without added cystine.

McCollum, Simmonds, and Parsons had reported that “ pea proteins are of very poor quality," but, according to Finks, Jones, and Johns, they identified their peas as Vicia sativa, which would mean that, strictly speaking, they were vetches.

Finks, Jones, and Johns say: "Some confusion of names has arisen between the cowpea, Vigna sinensis, and the field pea, Pisum sativum, and between the latter and the vetch, Vicia sativa, which is sometimes erroneously referred to as 'peas.'"

In the Southern states the cowpea (which is there the most extensively grown leguminous crop) is frequently called the field pea or simply pea. Botanically, however, the cowpea is more closely related to the bean (Phaseolus) than to the pea (Pisum). The true pea (Pisum sativum), largely grown in the Northern states and in Canada, consists of two groups of varieties, the sugar or garden peas whose seeds wrinkle when dry, and the field peas which remain smooth and round when dry. The former are grown only for human food and are used green; the latter are used as split peas and are also grown as a forage crop, particularly in Canada, and are therefore called Canada field peas.

The Vetch (Vicia sativa) is grown chiefly for forage; but one variety yields yellow seeds which are used to some extent as human food. Apparently it is these and not true peas that McCollum, Simmonds, and Parsons tested.

Finks, Jones, and Johns find the proteins of peas to be distinctly more efficient in nutrition than those of beans or cowpeas presumably also than those of vetches.

Pea meal has been shown by Osborne and Mendel to supplement satisfactorily the deficiencies of corn proteins (Journal of Biological Chemistry, Vol. 29, page 69).

Taking the fruits and vegetables as a whole, while often more economical as sources of energy and protein than is generally considered, yet they are even more significant for their ash constituents and for the vitamins which they contain.

The percentages of individual ash constituents in the edible