DUPLICATE HX00017108 E ' s ' ■/ . :••/ .^.■•••:^/ ;v:■^:';^.- 'M:&:-'^M.^ .^^■MW^^'^^- ■,'yi'j •''■ I 'j '•'•/ ' ■. t /Ivy.i «.v. i .!•,•"/ RF\A-\ Columljia ?Hmber£(itj? in tf)C Citp of ^eto gork CoQese of $i)psitctan£( anb burgeons; 3^ef erence Xibrarp Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/newerknowledgeofOOmcco THE NEWER KNOWLEDGE OF NUTRITION •The THE MACMILLAN COMPANY NEW YORK • BOSTON • CHICAGO • DALLAS ATLANTA • SAN FRANCISCO ly^ACMILLAN & CO., Limited LONDON • BOMBAY • CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA. Ltd. TORONTO THE NEWER KNOWLEDGE OF NUTRITION THE USE OF FOOD FOR THE PRESERVATION OF VITALITY AND HEALTH BY E. V. McCOLLUM SCHOOL OF HYGIENE AND PUBLIC HEALTH, TECE JOHNS HOPKINS UNIVERSITY ILLUSTRATED THE MACMILLAN COMPANY 1918 All rights reserved Copyright, 1918 By the MACMILLAN COMPANY Set up and electrotyped. Published October, 1918. Qt\m '/f/r PREFACE The need for knowledge of nutrition was never greater than at the present time when so large a part of the energies of the people of Europe and America are absorbed in the activities of war. The demoralization of agriculture over wide areas, to- gether with the shortage of tonnage for the trans- portation of food, have reduced the food supply of a number of nations to the danger point, and have cut off in great measure the opportunity for securing the variety which exists in normal times. The investigations of the last few years have, fortunately, led to great advancement in our knowl- edge of what constitutes an adequate diet. Such knowledge can, if rightly applied, greatly assist in enabling us to make use of our food supply in a manner which will avoid mistakes sufficiently serious to become reflected in a lowering of our standard of pubhc health. It seems certain that pellagra is the sequel to the adherence to a faulty diet for such a period as to materially reduce the powers of re- sistance of the body to infection, and reasons are presented in support of the view that there is a vi PREFACE much closer relationship between the character of the diet and the incidence of tuberculosis than has hitherto been believed. This view is offered in the present discussion as an invitation to criticism, in the hope that new data either in support or refuta- tion of its validity will be presented. If it shall be definitely proven that faulty diet is the chief factor in the etiology of this disease, and that pellagra, is, as the Thompson-McFadden Commission, Jobling and Peterson and others believe, caused by infection, it will establish that, as the author suggests, large groups of people are at the present time making serious errors in the selection of foods. Regardless of the outcome of future studies relating to the im- portance of diet to the etiology of these diseases, a non-technical presentation of the kinds of combina- tions of our natural foods which induce good or faulty nutrition in animals, should be of service in showing the inadequacy of the practice, which is still in vogue, of regarding calories as the factor of prime importance in the planning of the diet. From the data discussed in the following pages it will be evident that the idea that freedom of choice, and variety of food sources for the diet will prevent any faults in the diet from becoixdng serious, is no longer tenable, especially if one is willing to admit PREFACE vii the existence of many degrees of gradation of mal- nutrition, not recognizable except in their effects on the individual over a long period of time. The author recently enjoyed with a friend, a dinner which consisted of steak, bread made without milk, butter, potatoes, peas, gravy, a flavored gelatin dessert and coffee. The meal was appetizing and satisfying, but such a diet of seeds, tubers and meat would not promote health in an experimental animal over a very long period. The Hterature which has a bearing on the applica- tion of modern research to the practical problems of human nutrition has become somewhat extensive and is scattered in technical journals, and is not readily accessible, or easy to read in proper sequence. During the present year the author had the pleasure of presenting an interpretation of this literature in the Thomas Clarence Cutter Lectures at the Harvard Medical School. Believing that the pubhcation of these lectures would serve to answer many of the questions which have been asked in numerous letters from the public, they have been edited and presented in their present form. It is a pleasure to acknowledge the author's in- debtedness to those who have assisted in carrjdng out the experimental work which made possible the viii PREFACE discussion of nutrition offered in this book. Nearly three thousand feeding experiments varying in length from six weeks to four years have been observed. Special appreciation should be accorded to Miss Marguerite Davis who assisted with the early work, in the first two years of which no interpretation of the cause of success or failure of our experimental animals was possible, and to Miss Nina Simmonds and Miss Helen T. Parsons for their keen interest and never-failing loyalty to the work. E. V. McCOLLUM. The Johns Hopkins University School of Hygiene and Public Health, Baltimore, Md. CONTENTS CHAPTER PAGE I. The Biological Method for the Analysis of a Food-stuff 1 II. Experimental Scur\t and the Dietary Properties OF Vegetables 34 III. The Vegetarian Diet 53 IV. The Foods of Animal Origin 69 V. The Diseases Referable to Faulty Diet, or the So-called '"Deficiency Diseases" S3 \l. The Nursing Mother as a Factor of Safety in the Nutrition of the Suckling 116 VII. Practical Considerations wbich Should Guide in THE Planning of the Diet 130 Introduction to the Legends to the Charts . . . 154 Bibliography 191 Index 197 IX THE NEWER KNOWLEDGE OF NUTRITION THE NEWER KNOWLEDGE OF NUTRITION CIL\PTER I THE BIOLOGICAL METHOD FOR THE ANALYSIS OF A FOOD-STUFF Our knowledge of nutrition has progressed hand in hand with the development of the science of Chemistry. Chemical science gave us the clue to an understanding of the nature of the food-stuffs and the changes which take place in digestion, as well as an appreciation of some of the secrets of the metabohc processes which take place within the tissues of the body. Chemistry will continue, as time goes on, to aid in extending our knowledge of the finer processes of physiology. Nevertheless, it has been possible for a time to advance very rapidly in the study of nutrition, from the technical as well as from the practical standpoint, by a systematic feeding of simplified diets to animals. The results were interpreted on the observations as to the abihty, or failure, of the animals to develop normally, as the diets were modified. Progress has resulted in the past, and will continue in the future to come from the judicious division of labor between the 1 2 THE NEWER KNOWLEDGE OF NUTRITION study of food problems by chemical methods, and by animal experimentation. In this brief exposition of the present situation respecting our knowledge of foods and nutrition, it is desirable that the reader should appreciate the viewpoint of the investigator, and should understand the hne of reasoning by which the successive steps in the progress of the last few years have been attained. A brief historical account of the steps by which research in this field have been developed will serve this purpose, and at the same time, will illustrate the mental processes of a student engaged in the task of bringing order into a field of scientific inquiry where before there was no clear understanding. A plant structure, or an animal body is an exceed- ingly complex mixture of chemical substances, many of which are themselves individually as complicated in their structure as the most complex machine. The first step in the direction of reaching an under- standing of the chemistry of the living mass, must involve the separation and study of the structural units of which the tissues are composed. This was, indeed, the field of activity of many organic and physiological chemists during the nineteenth century. The fats and the simpler substances into which they can be converted as in soap making; the starches and the simpler sugars, and the manner in which they are related chemically; the proteins, bodies having the properties of egg white, the casein of milk, hair, etc., yet very closely related in their chemical nature, BIOLOGICAL ANALYSIS OF FOOD-STUFF 3 since they can all be resolved into the same digestion products in the animal body, or in the chemical laboratory, have all been carefully studied and wdth marked success. These and a long Ust of a thousand or more relatively simple chemical substances have been discovered, and isolated in a state of purity from plant and animal tissues. They have been studied to determine their special properties, composition and the tests by means of which they may be recog- nized and identified. Through a century of patient labor by many able men, an understanding of the number and character of simple structural units into which the tissues of ardmal or plant can be separated, became reahzed. Furthermore, certain of these smiple bodies could be recognized as intermediate products on their way toward being built up into the most highly organized units of the hving tissues; others were shown to be degradation products resulting from the physiological activity of the living tissues of the plant or ardmal. Through these studies it became established that the body of an animal or the tissues of a plant consists essentially of: proteins, which are peculiar in that they contain about sixteen per cent of the element nitrogen, and are complex in structure; starch-like substances and sugars, into which the starches can be easily converted, and fats and a number of closely related, and, in many respects, similar substances known collectively as lipoids. With these there are always associated in the hving tissues more or less 4 THE NEWER KNOWLEDGE OF NUTRITION water and a number of mineral salts. Numerous special varieties oi ^ach of these types of substances became known, and their less obvious characteristics were described. Certain substances were found to be special products, found only at certain times and in certain special locahties, and these became re- garded in their true light, as of subordinate interest. Examples of such are the alkaloids, quinine, strich- nine, etc., the cellulose which serves as skeletal tissue for the plant but is not necessary for the animal, and in the same category belong the waste products of the Ufe processes of the animal body, most of which are not found in plant substances. Living tissues, although always associated with numerous sub- stances, the exact importance of which could not be determined, were found to consist essentially of the proteins, fats, sugars, mineral salts and water. These came to be regarded even as early as 1840, as the essential and never failing constituents of plant tissues and were regarded as the essential constituents of an adequate diet for an animal. The processes of the digestion of food have excited the wonderment and have occupied the patient attention of some of the most earnest students of physiology and biochemistry. The chemistry of the fats, and the starches and sugars being simpler, or rather less complex than that of the proteins, came to be earher understood in their essential features. It was not until toward the close of the nineteenth century that the nature and extent of protein diges- BIOLOGICAL ANALYSIS OF FOOD-STUFF 5 tion became clearly appreciated. Soon after 1900 the researches of Fischer revealed the great variation in the composition of proteins from different som^es.^ This discovery introduced into nutrition studies the idea of quahty in addition to quantity which had heretofore seemed satisfactory to students of nutri- tion. Most proteins were found to be resolved into eighteen simple digestion products called amino- acids, and it was found that the proportions in which these were present in the protein molecule varied greatly in the proteins from different sources. All or nearly all of these digestion products appear to be indispensable constituents of an adequate diet. All natural foods contain several proteins as the extensive and valuable studies of Osborne have shown, ^ and although there are individual proteins which are entirely lacking in one or more of the essen- tial digestion products of proteins, every natural food appears to contain more or less of each of them. The proteins of any single food-stuff may be regarded as biologically complete, but their biological values differ greatly, depending upon the yield of the several amino-acids which can be obtained from them. Food Analysis. — Since proteins, carbohydrates, such as starches and sugars, fats and mineral salts came to be regarded as the essential constituents of the normal diet, it early became the principal activity of the investigator of nutrition problems to analyze foods of every sort by chemical methods in order to 6 THE NEWER KNOWLEDGE OF NUTRITION determine their content of what were supposed to be the only essential food complexes. Pronounced differences were observed in the composition of the many substances which serve as food for man and animals. Meats, milk, eggs, and a few seeds such as the pea and bean are very rich in protein, the cereal grains contain less of this food substance, whereas the tubers and vegetables, especially in the fresh condition, contain but very little. Equally great variations are observable in the water content of foods, and in their yields of fats and carbohydrates. One of the great epochs in the development of the science of nutrition, is that in which Atwater and his associates examined and tabulated in classified form the chemical composition of an extensive list of human foods. ^ Following this, similar data were accumulated in the Agricultural Experiment Sta- tions concerning substances used for anianal foods. Up to about 1900 the idea that there was any varia- tion in the quality of the proteins from different sources did not become generally appreciated. In the light of the revelations in the field of nutri- tion during the last few years, it seems remarkable that close students of animal nutrition accepted for so long, without proof, the belief ihat the results of a chemical analysis revealed the dietary values of food-stuffs. Disease and Diet. — Restricted diets of monotonous character have produced, for centuries, diseases in man in several parts of the world. The only one BIOLOGICAL ANALYSIS OF FOOD-STUFF 7 of these which was at all general in the Western hemisphere was scurv^^, a disease which caused much suffering among sailors in the days of the long saiHng voyages. It was well understood that the disease was the sequel to the consumption of a faulty diet, composed usually of biscuit and salt meats, and that prompt recovery resulted from the consumption of liberal amounts of fresh vegetables and fruits. Decades passed without any systematic attempt to determine the cause of the pecuhar value of this class of foods. Pellagra was a scourge among the poorest of peas- ants in parts of Europe for centuries, and its etiology has been referred b}^ many to the poor quality of the shnple and monotonous diet. This disease was not observed in Ajnerica until after 1900. Since then it has been steadily increasing in the Southern States. Beri-beri is a disease common among the poorest classes of the Orient, who limit their food supph^ principally to polished rice and fish. It is remarkable that not until the year 1897 was the first fertile suggestion made by Eijkman,^ as to the nature of the dietary fault which was responsible for the development of this disease. ]\Ian has been sufficient^ industrious in most parts of the world to secure for hunself a varied diet, derived from the cereal grains and legumes, fruits, roots and tubers, meats and certain leaves, which he found edible. Beginning with the da^\^l of the era of his most rapid advance toward achieve- 8 THE NEWER KNOWLEDGE OF NUTRITION ment, he has in many parts of the world been the possessor and protector of flocks and herds, which provided him with clothing, and a constant supply of both meat and milk. The importance of this last item in his food supply we have just now come to really appreciate. It is in order that it may be fully appreciated how great are the differences in the nutritive value of foods of such a composition as to appear alike from the results of chemical analysis that the present account of the investigations of recent years was prepared. In the year of 1907 the author began the study of nutrition problems at the Wisconsin Experiment Station. An inspection of the literature which re- lated to nutrition at that time disclosed the fact that the diet was supposed to consist essentially of pro- tein, carbohydrates and fats, and a suitable amount of several mineral salts. There were in the literature two papers which were highly suggestive that a new era was about to dawn in this field of research. Henriques and Hansen,^ believing that gliadin, one of the proteins of wheat, was free from the amino- acid lysine, had made up a diet of purified gliadin, carbohydrate, fats and mineral salts, and had at- tempted to nourish on this food mixture, animals whose growth was complete. It was reported that rats had been kept in a state of nitrogen equilibrimn, and even retention of nitrogen (protein) was reported during an experimental period covering nearly a month. In most of their trials th« animals failed BIOLOGICAL ANALYSIS OF FOOD-STUFF 9 steadily from the time they were confined to food of this character. Willcock and Hopkins ^ had conducted experiments with similar food mixtures, composed of carefully purified food-stuffs in which all the constituents were kno^^^l. When the protein of the diet consisted solely of zein, from maize, the mice lived but a few days. T^lien to this food the amino-acid trypto- phane, wliich is not obtained on the digestion of zein, was added to the diet, the animals hved dis- tinctly longer than without this addition. All ex- perimental work with such diets indicated that they were unable to support well-being in a young animal during growth over a prolonged period. It was an interest in these results, and a desire to know why such food mixtures, which comphed with all the re- quirements of the chemist and the dietitian, failed to properly nourish an animal that led to the decision that the study of nutrition offered a promising field of activity. At the Wisconsin Experiment Station there was in progress at that time an experiment which greatly strengthened the author's conviction that the most profitable point of attack for the study of the prob- lems of nutrition, lay in the study of greatly sim- plified diets so made up that every component should be kno^\^l. It seemed that, emplo^dng such diets, and by the systematic addition of one or more purified substances known to be found in natural foods, or in animal tissues, it should be possible to arrive at the 10 THE NEW^R KNOWLEDGE OF NUTRITION solution of the problem of just what chemical com- plexes are necessary in the diet of the liigher ani- mals. The above experiment was based upon earlier work by Professor S. M. Babcock, and was suggested by him, and carried out at first by Professors Hart and Humphrey, and later with the cooperation of Mr. Steenbock and the author."^ In this experiment the object w^as to determine whether rations, so made up as to be ahke, in so far as could be determined by chemical analysis, but derived each from a single plant, would prove to be of the same value for growth and the maintenance of vigor in cattle. The ration employed for one group of animals was derived solely from the wheat plant, and consisted of wheat, wheat gluten and wheat straw; for a second group the ration consisted entirely of com plant products, and included the corn kernel, corn gluten, a by-product of the corn starch industr^^, and the leaves and stalks of the corn plant (corn stover); the third group derived their ration solely from the oat plant, being fed entirely upon rolled oats and oat straw. There was a fourth group which it was supposed would serve as controls, which was fed a ration having the same chemical composition, but derived from about equal parts of wheat, corn and oat products. The animals employed were young heifer calves weighing about 350 pounds, and were as nearly comparable in size and vigor as could be secured. BIOLOGICAL ANALYSIS OF FOOD-STUFF 11 They were restricted absolutely to the experimental diets, and were well cared for. They were given all the salt (XaCl) they cared to eat, and were allowed to exercise in an open lot free from vegetation. Their beha\'ior during gi'owth, and in performing the func- tions of reproduction were extremely interesting. All gi'ouiDS ate practically the same amount of feed, and digestion tests showed that there was no dif- ference in the digestibihty of the three rations. It was not until the animals had been confined to their experimental rations for a year or more that distinct differentiation m then' ajDpearance was easily observable. The cox^n fed gi'oup were sleek and fine and were e\'idently in an excellent state of nutrition. In marked contrast stood the wheat fed group. These anmials were rough coated and gaunt in appearance and small of ghth as compared with those fed the corn plant ration. The weights of the two groups did not differ in a significant degi^ee. The groups fed the oat plant ration and the mixture of the three plants, leaf and seed, stood intermediate between the two lots just described. The assumption that the animals receiving the mixture of products would do better than any of the others, and thus serve as the standard gi^oup for controls was not realized. The corn fed animals were at all times in a better state of nutrition than were those receiving the greater variety of food materials. The reproduction records of these animals are of special interest. The com fed heifers invariably 12 THE NEWER KNOWLEDGE OF NUTRITION carried their young the full term, and the young showed remarkable vigor. All were normal in size and were able to stand and suck within an hour after birth as is the rule with vigorous calves. All lived and developed in a normal manner. The young of the wheat fed mothers were the reverse in all respects. All were born three to four weeks too soon, and all were small and weighed on an average forty-six pounds, whereas the young of the corn fed annuals weighed 73 to 75 pounds each. This weight is normal for new-born calves. The young were either dead when born or died within a few hours. The young of the mothers which had been grown on the oat plant were almost as large as those from the corn fed mothers, the average weight being 71 pounds. All of them produced their calves about two weeks too soon. One of the four was born dead, two were very weak and died within a day or two after birth, the fourth was weak, but with care it was kept alive. The young of the cows fed the mixture of the three plants were weak in most cases, and one was born dead and one lived but six days. The mothers were kept on their experimental rations, and the following year they repeated in all essential details the reproduction records observed in the first gestation period. Records were kept of the milk production during the first thirty days of the first lactation period. The average production per day by each individual in the corn-fed lot was 24.03 pounds; for the wheat- fed BIOLOGICAL ANALYSIS OF FOOD-STUFF 13 animals 8.04 pounds, and for the oat-fed animals 19.38 pounds. Those fed the mixture of the three plants produced 19.82 pounds of milk per cow per day during the first thirty days. In the second lacta- tion period the figures for milk production were 28.0; 16.1; 30.1; 21.3 pounds, respectively, per day during the first thirty days. Through autopsy and analysis of tissues of the young, and analysis of the feces and urines of the animals in the several gi^oups, an elaborate attempt was made to solve the problem of the cause of the marked differentiation of the animals fed these restricted diets. Interesting data were seciu-ed which showed marked differences in the character of the fat in the milk of cows from the different lots, and the observation was made that the urines of the wheat fed animals were invariably distinctly acid in reaction, whereas those from the other lots were alkahne or neutral to fitmus indicator. It was not possible by any means knowTi to physiological chem- istry, to obtain a clue to the cause of the pronounced differences in the physiological well-being of the different lots of cows. This experiment confirmed the author's conviction that the only way in which the problems of nutrition could ever be solved, would be to solve the problem of the successful feeding of the most simplified diets possible. If this were accomphshed it would be possible to proceed from the simple to the complex diets employed in prac- tical nutrition, ascertaining the nature of the dietary 14 THE NEWER KNOWLEDGE OF NUTRITION faults in each of the natural foods, singly, the seed alone, and the leaf alone before attempting to inter- pret the cause of malnutrition in animals fed the more complex mixtures. Such an undertaking as that just described, viz., the solution of the problem of why animals do not thinve on a diet of purified protein, starch, sugars, fats and inorganic salts which contained all the elements known to be left, as ash, on the incineration of an animal body, necessitated the employment of small laboratory animals. This was true for several reasons: First, because it is difficult and laborious to prepare isolated and purified food substances in sufficient amounts for the conduct of feeding experi- ments; second, it is both necessary and desirable to shorten the length of the experiments as much as possible, consistent with obtaining data regarding growth and reproduction, in order that data may accumulate sufficiently fast to make progress reason- ably rapid. The domestic rat seemed to be the most suitable animal, and accordingly it was selected. The rat has a gestation period of but 21 days, and the young are ready to wean at the age of 25 days. The female usually produces her first litter of young at the age of about 120 days, and will as a rule have five litters by the time she reaches the age of four- teen months, which age marks the end of her fertihty. The span of life of a rat which is well nourished is about 36 months. A^Tien such an animal is employed, it is possible to accomplish within a relatively short BIOLOGICAL ANALYSIS OF FOOD-STUFF 15 time, the accumulation of data regarding growth and reproduction which it would take years to secure with domestic animals of large size, long period of gestation and long span of life. A sufficient number of comparable experiments have now been conducted with several species of animals to make it appear certain that the chemical reciuirements of one species are the same as that of another among all the liigher anmials. The requu-e- ments ^\dth respect to the physical properties of the food vary gi^eatly. The ruminants must have bulky food with the right consistency, whereas the omnivora (man, pig, rat, etc.), cannot, because of the nature of their digestive tracts, consume enough of such foods as leaves and coarse vegetables, to meet their energy requirements. The early efforts to nourish young rats on diets composed of purified proteins, carbohydrates, fats and mineral salts, confirmed the results of the earlier investigators. The animals lived no longer on such food mixtures, than when allowed to fast. The rations employed w^ere of such a character that the most thorough chemical analysis could reveal no reason why they should not adequately nourish an animal. It seemed obvious that there was some- thing lacking from such mixtures which is indis- pensable for the nutrition of an animal, and a system- atic effort was made during the years that followed to discover the cause of failure of animals to develop on diets of purified and isolated food-stuffs. It was 16 THE NEWER KNOWLEDGE OF NUTRITION not until 1912 that light began to be shed upon the problem. The diet which was most in use at that time con- sisted of purified casein to the extent of about 18 per cent, lactose 20 per cent (supposed to be pure), about 5 per cent of some fat, together with a salt mixture which was made up in imitation of the min- eral content of milk, and the remainder of starch to make 100 per cent.^ This food mixture was sup- posed to be composed of materials sufficiently pure to comply with the requirements of such work; that is, they were supposed to contain too little of any impurities which would in any way influence the results. With this diet the interesting observa- tion was made that growth could be secured when the fat in the food mixture was butter fat, whereas no growth could be secured when the butter fat was replaced by lard, olive oil or other vegetable oils. Egg yolk fats were next tried and were found to induce growth in the same manner as butter fat. It was definitely established that, contrary to the past beliefs, the fats are not all of the same dietary value. Certain fats contain some substance which is not dispensable from the diet, whereas other fats do not contain the dietary essential in question. The portion of the food mixture other than fat, appeared to contain only substances of knowm com- position, i. e., protein, carbohydrate and inorganic salts, and for a time it appeared that the unknown substance in butter fat was the only element of BIOLOGICAL ANALYSIS OF FOOD-STUFF 17 myster}^ in the diet. The lactose or milk sugar was carefully examined as to its purity and was judged to be sufficiently pure to be satisfactory for such expermiental work, since it was practically free from nitrogen. The tentative conclusion w^as reached that the essential factors in an adequate diet included one substance or a group of substances which had not been appreciated in the past, and that these, if there should be more than one, w^ere associated with certain fats but not with all. This observation was in harmony \vith the pub- lished work of Stepp ^ which had appeared in 1909. Stepp observed that gro^^^l mice were satisfactorily nourished by a bread which was made with milk, but that early failure and death followed when the animals were fed the same bread which had been previously extracted with alcohol. ^Mien the sub- stances extracted from the bread by alcohol were replaced, the bread was again rendered efficient for the maintenance of life and health. He demonstrated in other experiments that the bread could be ex- tracted with ether or with chloroform ^\dthout re- moving the substance wliich was soluble in alcohol, and without which the animals steadily failed. Stepp considered the unknowm substance or sub- stances with which he was dealing in his feeding work, as belonging to the not well defined group of sub- stances generally called lipoids. This group includes fats and related substances more complex in char- acter, some of which contain the elements, phos- 18 THE NEWER KNOWLEDGE OF NUTRITION phorous and nitrogen. Stepp was not able to secure with any knowTi lipoid, the effects which resulted from the administration of the alcohol-soluble por- tion of his milk bread. A new viewpoint was suggested by F. G. Hopkins of Cambridge, England, in 1912.^^ He had as early as 1906 conducted experiments in the feeding of mix- tures of purified protein, carbohydrate, fats and mineral salts and was aware of the fact that neither maintenance of body weight, nor growth could be secured with such diets. He then tried the addition of such amounts of milk as would furnish 4 per cent of the total dry matter of the food mixture and ob- served that growth could proceed when such milk additions were made. Hopkins suggested the exist- ence of certain unidentified food substances which were supplied by the milk and to these he gave the name '^accessory" articles of the diet. Attention has been called to the fact that Eijk- man, a student of the disease, beri-beri, made the discovery in 1897 that pigeons fed solely upon pol- ished rice, develop usually within three or four weeks, a state of paralysis which is called pol^meuritis, and is analogous to beri-beri in man. He found that when the birds were given the entire rice kernel, or unpolished rice the disease did not develop. It was found, furthermore, that the administration of rice pol- ishings to pigeons suffering from polyneuritis, caused prompt relief of their symptoms. Eijkman's ob- servations attracted little attention until 1911, when BIOLOGICAL ANALYSIS OF FOOD-STUFF 19 Funk took up the study of beri-beri, and made an elaborate attempt to isolate and study the ''curative " substance in rice pohshings.^^ Fraser and Stanton had, however, in 1907, employed alcohohc extracts of rice polishings for the relief of experunental poljTieuritis.^- In the work of these investigators the erroneous assumption seems to have prevailed that the process of pohshing consists essentially of the removal of the outer covering, or bran layer of the rice kernel. As a matter of fact the rice germ is in a very exposed position, and is easily rubbed off during the process of polishing. As was later shown by ]\IcCollum and Da\4s, for the wheat kernel, the germ is a very different thing from the seed from the dietary standpoint. ^^ The reason for this will be made clear later. The studies of Eijkman, Hopkins, Fraser and Stanton and Funk, referred to above, clearly sug- gested that there was required in the diet something other than protein, carbohydrate, fats and inorganic salts. ^Alien jNIcCollum and Davis succeeded in securing growth in young rats fed upon a mixture of ''purified" food-stuffs, when the mixture contained butter fat, but no growth when vegetable fats or the body fats of animals were substituted, it appeared to them that the only element of mystery in the diet was that associated with certain fats. This could not at first be harmonized with the observation of Funk, namely, that butter fat had no favorable influence on pigeons which were suffering from ex- 20 THE NEWER KNOWLEDGE OF NUTRITION perimental beri-beri.^'' His studies seemed to in- dicate that there is necessary in the normal diet at least one other substance, the absence of which brought on the attack of polyneuritis. Later experi- ments by McCollum and Davis cleared up the prob- lem, but not without a considerable amount of experimenting and delay. McCollum and Davis arrived at the conclusion that aside from the long recognized constituents of the normal diet, there is some unknown substance in butter fat which must likewise be furnished in the food, and began a systematic investigation of the problem of why a young animal cannot grow when restricted to a single grain such as wheat, maize (corn), oats, peas, beans, etc. They had tried many times to limit young rats to whole wheat, or other grain as their sole food, and had found that they not only failed to grow, but would not live many weeks. Chemical analysis shows the cereal grains to contain all the essential food substances, for which we know how to analyze, viz : proteins, starch, sugar, fats and all the mineral salts which occur in the body of an animal. It was reasoned that, since all the dietary essen- tials, except possibly the one which is not present in vegetable fats, are certainly present in the wheat kernel, the faults in the latter must depend upon a lack of the unknown substance contained in butter fat, or on the quality of some one or more of the well recognized constituents of the diet. It seemed BIOLOGICAL ANALYSIS OF FOOD-STUFF 21 possible to discover by means of a systematic series of feeding experiments in which the quahty of the seed should be improved with respect to one dietary factor at a time, which factor was interfering with growth. Accordingly the^^ fed wheat in the following combinations, and with the results noted: (1) WTieat alone no growth, short life. (2) Wheat plus purified protein no growth, short life. (3) Wheat plus a salt mixture wliich gave it a mineral content similar to that of milk very little growth. (4) Wheat plus a gro\\i:h promoting fat (butter-fat) no growth. From these results it seemed apparent that either their working hypothesis regarding the factors which are necessary in an adequate diet, must be wrong, or there must be more than a single dietary factor of poor quality, and jointly responsible for the poor nutrition of the animals. In order to test this theory they carried out another series of feeding experiments, in which wheat was fed, supplemented with two purified food additions. (5) Wheat plus protein, plus the salt mixture Good growth for a time. Few or no young. Short life. (6) Wheat plus protein, plus a growth-promoting fat (butter- fat) No growth. Short life. (7) Wheat plus the salt mixture^ plus the growth-promoting fat, (butter-fat) Fair gi'owth for a time. Few or no young. Short life. 22 THE NEWER KNOWLEDGE OF NUTRITION The behavior of the animals fed wheat with two purified food additions was highly suggestive that there are three dietary factors of poor quality in the whe^-t kernel. This was demonstrated to be true by a feeding trial in which wheat was fed with three purified food additions: (8) Wheat plus protein, plus the salt mixture, plus a growth- promoting fat (butter-fat) .... Good growth, normal number of young, good success in rearing young; life approximately the normal span. McCollum and Davis were, in 1912, more than ever convinced that the only element of mystery in the normal diet was the unidentified substance in butter fat, for with the improvement of three dietary factors wheat became a satisfactory food for the nutrition of an animal during growth and for the support of all the functions of reproduction and rearing of young. This series of experiments brought to light two new viewpoints in animal nutrition, one of which was, that the inorganic content of the wheat kernel, although it furnishes all the necessary elements, does not contain enough of certain of these to meet the requirements of a young animal during the growing period. It is true that some years earlier Henry, ^^ had called at- tention to the deficiency of the corn kernel in ash constituents, and had in some of his experiments BIOLOGICAL ANALYSIS OF FOOD-STUFF 23 added wood ashes to the diet, with noticeable im- provement in the well-being of the animals. The fact that seeds such as wheat fail to supply enough of any of the essential inorganic elements was not geneially appreciated and was given but Httle at- tention in works on nutrition. Later, work by Mc- Collum and Simmonds, demonstrated that the de- ficiency in mineral elements in wheat and other seeds is limited to thi^ee elements, calcim, sodium and chlorine. A second new viewpoint brought out by these ex- periments was the fact that the wheat kernel is indeed too poor in its content of the unidentified substance which butter fat contains, to satisfactorily nourish an animal over a long period of time. It has already been mentioned that the studies of Kossel, Fischer and of Osborne, had made it clear that there should exist very pronounced diffei'ences in the value of the proteins from different sources. The proteins were prepared in a state of relative purity and were digested in the laboratory by means of acids, and were analyzed by the methods of Fischer and of Kossel. Certain of the eighteen di- gestion products, the amino-acids, were determined quantitatively sp far as the methods would permit. Although the methods were never perfected so as to give results which w^ere approximately quantitative, except in the case of less than a third of the amino- acids which were known to be formed in the di- gestion of proteins, it was shown in the case of these 24 THE NEWER KNOWLEDGE OF NUTRITION few that there were very great variations in the pro- portions among them in the mixture obtained from proteins from different som-ces. Thus the proteins of the muscle tissues of several species of animals were sho^^^l to yield between 12 and 14 per cent of glutamic acid, one of the digestion products obtained from practically all proteins. The same amino-acid is present in the two principal proteins of the wheat kernel to the extent of about 40 per cent of the total protein. These two proteins together make about 85 per cent of the total protein of the wheat kernel. Other equally great differences were shown to exist in the composition of proteins of our common food-stuffs and those of the tissue proteins which are formed during growth. A good illustration of the problems which the animal meets in its protein nutrition, may be had by comparing the digestion products of the protein molecule to the letters of the alphabet. The pro- teins of the food and of the tissues are made up of the same letters arranged in different orders and present in different proportions. In growth the animal takes as food, proteins which are very unlike those of its tissues, digests these into the simple com- plexes, the amino-acids, and then, after absorbing these, puts together the fragments in new order, and in new proportions to form the tissue proteins. If the muscle tissue of an animal be likened to a block of printer's type so arranged as to print the rhyme beginning ''Jack Spratt, who could eat no BIOLOGICAL ANALYSIS OF FOOD-STUFF 25 fat, and his wife could eat no lean," the proteins of which the muscle consists are represented by the mdividual words, and the digestion products of the proteins by the letters of which the words consist. Now if the aniinal could take in its food proteins which correspond to a block of type which would print the jingle beginning: ''Peter Piper picked a peck of pickled peppers," it is easy to understand that when the proteins of the food are resolved to their constituent letters, and an effori made to form the body proteins of the new and different t^'-pe from the letters supplied by the food, the trans- formation cannot be made. In setting up the first line, '"'Jack Spratt could eat no fat and his wife could eat no lean/' we need four of the letter t, but the food proteins contain but one. The first line of the Jack Spratt rhyme, which represents the muscle proteins, requires but one letter p, whereas the food proteins represented by the Peter Piper rhyme yield nine in the first line. The first line of the Jack Spratt rhyme contains the letters j and n, whereas the Peter Piper rhyme contains none, so that even with the entire stanza: Peter Piper picked a peck of pickled peppers If Peter Piper picked a peck of pickled peppers, Where's the peck of pickled peppers, That Peter Piper picked? it is not possible to reproduce even the first line of the Jack Spratt rhyme, and in order that gi'owth 26 THE NEWER KNOWLEDGE OF NUTRITION might become possible, it would be necessary to take proteins of another character, which would supply the missing letters. Such a comparison between food proteins and tissue proteins gives a good illustration of the kind of problem which the animal meets in its protein nutrition. The most conspicuous protein of the corn kernel (zein) is wholly lacldng in tlu-ee of the amino- acids or digestion products which are obtainable from most tissue proteins. In accord with what we should expect on theoretical grounds, this protein is, when taken as the sole source of amino-acids, not capable of supporting growth, or of maintaining an animal in body weights This illustration shows how we m.ay have excellent, good or poor food proteins for the formation of body proteins in gi^owth. The investigations described above, the object of which was to find the cause of the failure of an anmial to grow when restricted to wheat as its sole source of nutriment, w^ere carried out in 1912, the year following the publication of the first work by Funk on polyneuritis. In the same year Hop- kins called attention to the remaiivable effects pro- duced by the addition of small amounts of milk to diets composed of purified food-stufTs. The 'Sdta- mine'' hypothesis had just been formulated by Funk.i*^ McCoUum and Davis were, therefore, aware of the relation of a diet of polished rice to experi- mental beri-beri. They believed, in the light of their experiences with the diet of purified protein, BIOLOGICAL ANALYSIS OF FOOD-STUFF 27 carbohydrate, fats and inorganic salts, which, they observed, was capable of inducing growth when cer- tain fats were supplied, but not when others were substituted, and the- further fact that wheat could be supplemented by purified protein, a growth- promoting fat, and a suitable salt mixture, i. e. with food-stuffs of knowTi character, that there was but a single unidentified substance necessaiy in the diet. They decided to next apply to polished rice the same procedure which had shown so clearly the nature of the dietary deficiencies of wheat. Rice, thcA^ reasoned, could be nothing less than a mixture of proteins, starch, traces of fat, and a mixture of inorganic salts, similar to that contained in wheat, but smaller in amount. It should, therefore, be supplemented ^^dth a suitable salfc mixture, a purified protein, and a growth-promoting fat, so as to in- duce gi'owth and maintain animals for a long time in a state of health. This seem.ed to be a necessaiy conclusion, since they had secured growth and well- being in animals fed strictly upon a mixtme of puii- fied protein (casein), starch, milk-sugar, butter fat and a mixture of inorganic salts of suitable com- position. It was a great surprise to jMcColIum and Davis to find that polished rice, even when supplemented with the purified protein, casein, butter fat and a salt mixture properly constituted, failed utterly to induce any growth in young rats.^^ Not only did they fail to grow, but in the course of a few weeks 28 THE NEWER KNOWLEDGE OF NUTRITION they developed in some cases a state of paralysis which was suggestive of polyneuritis. Here was an apparent contradiction. The poUshed rice could be nothing less than a mixture of protein, carbohydrate and salts. The only difference between this and the mixture of supposedly purified food-stuffs with which they had achieved success was in the 20 per cent of milk sugar w^hich the latter contained. It was, therefore, decided to repeat the experiments with the latter mixture, with the milk sugar replaced by starch. It was found that this change in the com- position of the food mixture made the difference be- tween success and failure. No growth could be se- cured w^hen the milk sugar was omitted. Later experiments showed that if milk sugar was suf- ficiently purified by repeated crystallization it was no longer effective in inducing gi'owth w^hen added to the purified food mixture, whereas the water from which the sugar had been crystalHzed would, w^hen evaporated upon the food mixture, render it capable of inducing growth. This made it evident that there is indeed a second dietary essential, of which an animal needs but a very small amount, but which is absolutely necessaiy for both growth in the young and the maintenance of health in the adult. FuHher experiments were then conducted to find whether this unidentified substance which w^as being added accidentally as an impurity in the milk sugar, was the same as the substance which Fraser and Sta: ton and Funk were dealing with in their studies BIOLOGICAL ANALYSIS OF FOOD-STUFF 29 of beri-beri. It was found that pigeons which had developed beri-beri as the result of being fed ex- clusively upon polished rice, could be temporarily ''cured" with any preparation which would, when added to the diet of purified food-stuffs, containing a gi'owth-promoting fat, cause animals to gi'ow. Follo^^'ing the method introduced by Fraser and Stanton, ]\IcCollum and Davis, ^^ next employed alcoholic extracts of various natural foods, adding the alcohol soluble matter to the standard mixture of purified protein (casein), starch (dextrinized), salts and butter fat, and soon became con^dnced that the substance which relieves the condition of pol>Tieuritis in pigeons was always present in the preparations wliich render the purified food mixture capable of promoting growth. They finally adopted an alcoholic extract of wheat germ as a source of this dietary factor in their investigations. Funk and his co-workers had previously shown that the curative substance is present in many natural foods. ^^ Repeated trials showed that the inclusion of the alcoholic extract of wheat germ or of other food, was not sufficient to induce growth unless the butter fat was likewise added to the purified food mixture. Both the growth-proinoting fat and the trace of unidentified substance in the alcoholic extract of wheat germ are necessary for the promotion of growth or the preservation of health. It has been pointed out that Funk, in his examina- tion of the vai'ious natural foods for the purpose of 30 THE NEWER KNOWLEDGE OF NUTRITION determining the distribution of the antineuritic sub- stance (substance which reUeves polyneuritis) found butter fat ineffective. This was later confirmed by McCollum and Kennedy. ^^ Through the '^vitamine" hypothesis, Funk at- tempted to account for the diseases beri-beri, scurvy, pellagra and rickets, as being each due to the lack of a specific chemical substance, a ''vitamine," in the diet.^^ This was a very logical conclusion from the data available to Funk. Scurvy, it had long been known is relieved in a very spectacular manner by the inclusion of fresh vegetables or orange juice in the diet, and there was no doubt that the disease developed as the result of a diet of poor quality. On first consideration it seemed very reasonable to assume that there is an ''antiscorbutic vitamine'^ in certain fruits and vegetables. Pellagra has long been suspected of being due to faulty diet, although the exact manner in which the diet is unsatisfactoiy remained obscure. It was generally appreciated by clinicians that a change to a highly nutritious diet in which milk and eggs were conspicuous was the best prophylactic measure for the treatment of the disease, and that without diet- ary measures, all remedies fail. It was not surpris- ing that Funk should have regarded pellagia as one of the ''deficiency" diseases, due to lack of a "vita- mine" in the diet. As will be shown later (Chapter V) there has since been secured much experimental evi- dence in support of the view that scurvy and pellagra BIOLOGICAL ANALYSIS OF FOOD-STUFF 31 do not arise from deficiency in the diet of specific chemical substances in the sense in which Funk suggested. This seems to be true also of rickets. In view of the considerations just mentioned rel- ative to the cause of scurvy and pellagra, and the convincing evidence that beri-beri is actually caused by specific starvation for a substance, "\dtamine," as Funk suggested, McCollum and Davis formulated in the following way, their working hypothesis as to w^hat constitutes an adequate diet. The diet must contain, in addition to the long recognized dietary factors, viz: protein, a source of energy in the form of proteins, carbohydrates and fats; a suitable supply of certain inorganic salts, two as yet unidentified substances or groups of substances. ^^ One of these is associated with certain fats, and is especially abundant in butter fat, egg yolk fats and the fats of the glandular organs such as the hver and kidney, but is not found in any fats or oils of vegetable origin. The second substance or group of substances of chemically unidentified nature, is never associated with fats or oils of either animal or vegetable origin. It is widely distributed in natural foods, and can be isolated in a concentrated, but not in a pure form, from natural food-stuffs by extraction of the latter with either water or alcohol. This water or alcohohc extract always contains the substance which cures pol}meuritis. At the time it seemed possible that it also contained several other ''vitamines," pro- tective against the other diseases mentioned. The 32 THE NEWER KNOWLEDGE OF NUTRITION former substance or group of substances, which is associated with certain fats is not '^curative" for any of the Ust of diseases which Funk designated as '^vitamine" deficiency diseases. Indeed, butter fat, which is the food containing one of the indispensable substances in greatest abundance, was stated by Funk to contain no ^^vitamine." ^^ Nomenclature of the Unidentified Dietary Essen- tials. — The ending amine has a definite and specific meaning in organic chemistry, and apphes only to substances containing the element nitrogen. Since butter fat, which is very rich in one of the dietary essentials in question is practically, if not entirely, free from nitrogen, it seems almost certain that the physiologically indispensable substance which it con- tains is free from nitrogen, and could not with pro- priety be designated by any name ending in amine. For this reason, and because it is possible to divide the unidentified constituents of the normal diet into two classes on the basis of their solubility, McCollum and Kennedy ^^ proposed the terms fat-soluble A and water-soluble B to designate them. The former prevents the development of a pathological condition of the eyes,^^ the latter prevents the development of beri-beri. As will be shown later, there is much evidence for and none against the view that what we designate by each of these terms is in reality but a single physiologically indispensable substance and not a group of substances. This necessitates the further assumption that certain of the diseases of BIOLOGICAL ANALYSIS OF FOOD-STUFF 33 dietary origin, which Funk held to be due to ^^vi- taniine" starvation, are in reahty due to other causes. This view will be supported by further evidence later. Indeed it is not possible to longer regard scurvy as a ^'vitaniine" deficiency disease. The ^Sdtamine" hypothesis of Funk was extremely attractive and seemed to account for the etiology of several diseases in a most satisfactory way. It seemed to rest upon sound observations, but in reality it rested only upon suggestive chemical ev- idence. It failed to stand the test of a systematic investigation of all the more important natural food-stuffs, by the biological method which was described in its essential features in illustrating the nature of the dietary deficiencies of the wheat kernel. CHAPTER II EXPERIMENTAL SCURVY AND THE DIETARY PROPERTIES OF VEGETABLES McCollum, Simmonds and Pitz ^ sought to test the vaUdity of the ''vitamine" hypothesis in its relation to scurvy, by an indirect method. The next logical step in the investigation of the possible num- ber of dietary essentials of unknown chemical nature which occur in the growth-promoting fats (fat- soluble A), and in the preparations which are never associated with fats (water-soluble B), seemed to be to study the oat kernel. There seemed much reason to beUeve that this seed would prove to be unique among the ordinary seeds in its dietary properties. Theobald Smith ^ had, in 1895, called attention to the fact that a diet of oats would cause in guinea pigs the development of a condition suggestive of scurvy. In 1909 Hoist and his co-workers in Sweden ^ de- scribed numerous experiments involving the produc- tion and relief of experimental scurvy in the guinea pig. Hoist observed that when this animal is re- stricted to a diet of oats it rarely fails to develop scurvy within a few weeks. The disease which is so produced is strikingly suggestive of scurvy in man. There is pronounced swelling of the knee and elbow joints, with rupture of the capillaries at these sites, 34 DIETARY PROPERTIES OF VEGETABLES 35 and there is also a spongy and hemorrhagic condition of the gums. Hoist stated that the disease was due to a deficiency of the oat kernel in an antiscorbutic substance, which is relatively unstable when manipulated in the lab- oratory. Milk was stated to be efficient for the cure of the disease induced by an oat diet, provided it was raw or had not been heated to very high tempera- tures. ]\Iilk wliich had been heated to 90° C. for ten minutes was said to be still effective, but boiled milk failed to induce a cure. Raw cabbage was stated to be highly efficient as a remedy against the disease in the guinea pig, whereas cooked or dried cabbage had lost most of its antiscorbutic property. In view of these observations, it seemed that, if it were true that scur\^ is as Funk and Hoist be- lieved, a disease resulting from ^^vitamine" defi- ciency, the oat kernel should prove to be a natural food-stuff v/hich lacked the antiscorbutic '' vitamine" but contained the anti-beri-bei i, and perhaps, also, the anti-pellagra and ot her ' ^ vitamines. ' ' McCollum, Smmaonds and Pitz^ submitted the oat kernel to the systematic procedure of the biological method of analysis, feeding it as the sole source of nutriment, and also with single and multiple additions of purified food substances, employing the rat as the experi- m^ental anhnal. This showed that the oat kernel (rolled oats) can be supplemented by the addition of a salt mixture of appropriate composition, a growth- 36 THE NEWER KNOWLEDGE OF NUTRITION promoting fat, and the purified protein gelatin, so as to induce growth at the maximum rate in young rats from weaning time to the full adult size, and sup- ported the production of a few young. WTien any one of these additions is omitted, the animals fail to develop. The oat kernel, therefore, contains all the dietary essentials in bhe water-soluble group (provided there is more than one such substance). Like wheat it lacks a sufficient amount of the fat- soluble A to support noi'mal nutrition. It was impossible to harmonize the results described by Hoist in the production of experimental scurvy in the guinea pig with those of McCollum, Sinamonds and Pitz, in which the rat served as the experimental animal, without making assumptions which would gi^eatly compUcate the w^hole subject of nutrition investiga- tions. There were serious discrepancies in the ex- perimental data from different sources. Hoist's studies pointed to the existence in the normal diet of a substance or substances of unknown character, which were easily destroyed by heat or by dessica- tion, and which act as protective agents against scurvy in the guinea pig, and appeared to demon- strate that the supposed antiscorbutic substance or substances w^ere absent from the oat kernel. The studies with the rat demonstrated beyond con- troversy, that at least for the rat, the oat kernel is deficient as a food only as respects the factors, in- organic salts, fat-soluble A, and in a lesser degree in DIETARY PROPERTIES OF VEGETABLES 37 the quality of its protein. When these factors are corrected, the oat kernel becomes a complete food for this species. Scurvy has been produced experimentally by faulty diet in the guinea pig, and is not known to occur in any species other than man and the guinea pig. If the explanation of Hoist and of Funk is cor- rect that scur\y is the result of the lack of a specific substance in the diet, it becomes necessary to make the further assumption that man and the guinea pig require this substance, since both suffer from the disease, whereas other species, as the rat, do not re- quire this complex as a dietary component. The only alternative is to conclude that scur\^ is in realty not a ''deficiency" disease in the sense in which Funk and Hoist employed the term. That there is actually no such unstable ''antiscorbutic substance" or "antiscorbutic vitamine" as postu- lated by Hoist and Funk, has been demonstrated by the studies of IMcCollum and Pitz.^ The proof of this is given m Chapter V. In the same chapter will be discussed the other so-called ''vitamine" deficiency diseases, pellagTa and rickets, and the character of the diets which play a part in their etiology. The data available supports the view that among the hst of so-called " deficiency " diseases, beii-beri, scur\^^ pellagra and rickets, only the first is due to the lack of a specific protective substance, Funk's "vitamine," or water-soluble B in the diet. The others are at least in some degree the result of faulty diets, but not 38 THE NEWER KNOWLEDGE OF NUTRITION in the sense in which Funk and Hoist employed the term ^'deficiency." McCollum and Simmonds have pointed out, however, that in the pathological con- dition of the eyes, known as xerophthalmia, of dietary origin mentioned above, we have a second deficiency disease, analogous to beri-beri.^ All the facts at present available point, therefore, to the beUef that what McCollum and his co-workers term water- soluble B, is in reality but a single physiologically indispensable substance.^ There is no evidence in support of the \dew that the term fat -soluble A need be considered as applying to more than a single chemical substance. Xeropthalmia of dietary origin will be described later (Chapter V). Similarity of the Seeds from the Dietary Standpoint. — By the application of the biological method of analysis of a food-stuff to each of the more im- portant seeds employed in the nutrition of man and anim.als, the fact w^as brought to fight that, they all resemble each other very closely in their dietary properties. The list of seeds examined included, — wheat,^ corn,^ rice,^^ rolled oats, rye,^ barley,^ kaffir corn,^ millet seed,^^ flaxseed, ^^ pea^^ and both the navy^^ and the soy bean.^ These all contain proteins which are of distinctly lower biological value for growth than are the proteins of milk ; they all are too poor in the same three inorganic elements, calcium, sodium and chlorine. All are, with the exception of millet seed, below the optimum in their content of the dietary factor, fat-soluble A. These three diet- >, .i >5 c ^ >, c c3 o 55 2 bC -d rt ^ 3 c ^ o 2 o 02 2 CD o3 .2 03 -t^ o ■+^ >> 1 E- S _3 "E g u, -t-= o -*-^ P aj 77^ ^ ^ o3 33 "^ O "E «4^ (4-1 c ;^ ;_ m d o c X -M o tK ^ -^ •i-l «*-! :3 ^** fl .s c ri ^ T3 S (U ? ^ G bC D tn ^ c3 bp O o bb 'C a O ^ ^ 3 a o3 bC M _o o3 fl cc c ii sc (K -«-3 c O <4-| o o c3 E, I3 ^ o CO O « ^ C3 g « so ^^ a ■N :2 DIETARY PROPERTIES OF \^GETABLES 41 suited in enormous econoixdc loss to farmers who have attempted to keep growing pigs in a dry lot and feed them cereal grains and by-products derived from these, as the sole source of nutriment. Little gi'owth can be secured under these chcmiistances, and the reason becomes clear from what has been said above concerning the nature of the dietary deficiencies of the seeds and the similarity of the seeds from the dietary standpoint.* It was a great surprise to ]\IcCollum, Simmonds and Pitz ^- to find that appropriate mixtures of leaf and seed make fairly satisfactory food mixtures for the support of growth, whereas, as has been stated, they were unable to secure any appreciable growth in animals fed exclusively on seeds and seed products, the drinking water supphed being distilled and there- fore salt free. The fii'st leaf which was studied was that of the alfalfa plant, for the reason that the ground, mmiature alfalfa plant is extensively^ mar- keted as a supplementaiy feed for pigs, and tlii'ough the courtesy of the Petei^ ^lilhng Company of Omaha, Nebraska a product ^'alfaha flour'' was made available in a convenient form. This consists * It Ls not to be understood from tliis that it is intended to imply that no increase in body weight can be secured in hogs when they are confined strictly to grain mixtures. They may indeed become very fat, and therefore apparently grow for a time on such foods as corn alone. Even under farm conditions, where they are able to secure a supplementary mineral supply through the water they drink and through the consumption of soil with the grain, there is httle growth in the sense that the muscle and organ tissues increase in volume. 42 THE NEWER KNOWLEDGE OF NUTRITION of the dry, immature leaf of the plant ground to a very fine powder of a bright green color. A series of diets consisting of seed, 60 per cent, and of alfalfa leaf flour, 40 per cent, were first fed to growing rats. The seeds employed, included wheat, corn, rolled oat, rye, millet seed, kaffir corn, pea and bean. The degree of success in inducing growth with most of these simple mixtures of one seed with the alfalfa leaf is much greater than can ever be secured with even such complex mixtures of seeds as corn, wheat, oat, hemp seed and millet seed in equal proportions. The latter mixture can support a fair amount of growth when its inorganic defi- ciencies are made good, but without mineral addi- tions almost no growth can be secured. Chart 6 shows typical growth curves which give an accurate idea of the relative values for growth of several combinations of the alfalfa leaf with seeds. Among the seeds with which studies have been made, the oat is best supplemented by the alfalfa leaf. A simple mixture of rolled oats, 60 per cent, and alfalfa leaf, 40 per cent, induces nearly normal growth to the adult size in the rat and induces a fair amount of reproduction and rearing of young. However, the animals fall considerably below the maximum performance in both these respects. An examination of other leaves of plants showed that the latter can in a general way be classed to- gether as food-stuffs of similar character, since they resemble each other more or less closely, just as the 02 OJ ^ -^ 3 • 1-1 -^j -fj o c3 CD o3 o :73 03 ^ T3 o o3 -tJ O o3 -G O ^1 rG ri ^ .w o ^ O 0) CO b .22 O o3 'C >< O «^ CO bC g fcH O p^ CO 03 ^^ c3 o3 02 ^ ?3 02 ^ bO « '§ .2 'S ^ -o fe T3 O > "C o3 =^ « O «^ O c3 03 »^ ^ S fe ^ O O cu o 43 -is ^ o 3 ^ C 'd -*^ .2 g S .ti 3 o -So'" bC 03 "^ ^ ^ > DIETARY PROPERTIES OF ^^GETABLES 43 seeds all resemble each other in their dietary prop- erties. The leaf proves to be a very differenfc thing from the seed from the dietary standpoint. The dry leaf usually contains from three to five times as much total ash constituents as does the seed, and is always especially rich in just those elements in which the seed is poorest, viz., calcium, sodium and chlorine. It follows, therefore, that the leaf supple- ments the inorganic deficiencies of the seed. The leaf, in most cases, contains much more of the dietary essential, fat-soluble A, than is found in any seed, so that combinations of leaf and seed prove more satisfactoiy for the nutrition of an animal than do mixtures of seeds alone. The leaf contains protein and amino-acids which result from digestion of pro- teins as does the seed. The amount varies from 8 per cent of protein (nitrogen X 6.25) in such fleshy leaves as the cabbage, after drying, to more than 15 per cent m the dr>^ alfalfa or clover leaf. The seeds vsiry in their content of protein from about 10 to 25 per cent. The leaf proteins appear, from the data available, to supplement and enhance in some degree the value of the seed proteins ^vith which fchey are combined. The leaf supplements, therefore, all the nutritive deficiencies of the seed, but not necessarily in a highly satisfactory manner. It is interesting to reflect upon the reasons why the leaf of the plant should show such decided dif- ferences in its nutritive properties as contrasted with the seed. A consideration of the difference in 44 THE NEWER KNOWLEDGE OF NUTRITION function of the two gives the clue to the cause. The seed consists of a germ, which forms in most cases but a very small part of the entire seed, together with a relatively large endosperm. The germ con- sists of living cells, which respire and are capable of multiphcation (germination) when the conditions are favorable. In the wheat kernel the germ con- stitutes about 5 per cent of the entire seed. The endosperm, on the other hand, consists largely of reserve food materials such as protein, starch, sugars, fats and mineral salts. It is not living matter, and contains few cellular elements. The endosperm is, therefore, in most respects comparable to a mix- ture of purified food-stuffs. There is, as experiments have abundantly demonstrated, relatively little of the dietary factor, water-soluble B, in the endosperm, and relatively much in the germ or embryo. The same is true for the second unidentified dietary factor fat-soluble A. This is practically absent from the endosperm, but is fairly abundant in the germ. Since the latter represents so small a portion of the entire seed, the seed itself is too poor in this sub- stance, in nearly all cases, to supply the needs of a growing animal. The leaf of the plant, on the other hand, is very rich in cells, and in most cases contains but Uttle re- serve food material. It is the laboratoiy of the plant. Chlorophyll, its green pigment, enables it to make use of the energy of the sunhght, and from the carbonic acid gas which it absorbs from the air, DIETARY PROPERTIES OF \^GETABLES 45 together with water and mineral salts, which it absorbs from the soil thi'ough its roots, it builds up proteins, starch, sugars and fats, which are used for the growth of new plant tissue, or for storage in the seed, tuber or other storage organs. The sur- faces of the leaf are a mosaic of living cells. They contain all the chemical complexes which are nec- essaiy for the nutrition of the animal cells, and are qualitatively complete foods. The quality of the leaf from the dietary standpoint may vary to a considerable extent. Some lea\xs are thin cellular structures, which diy easily in the sun when separated from the plant. In others, as the cabbage, the leaf is in some degree modified as a storage organ, and contains a considerable amount of sugars. The cabbage leaf likewise contains more than the ordinary amount of cellulose, which is its skeletal tissue. Its dietary properties are modified by these pecuharities in that the cellular elements are diluted by the more inert tissues and reserv^e food substances in the leaf. The freer a leaf is from the function of a storage tissue, the more intensified wiU be its leaf properties as a food. The fleshy leaves tend to have in some degree the dietaiy properties of the seed, and stand intermediate between the leaves, which ax-e thin, and dry easily, and the seed in this respect. The Tubers. — After the seeds, the tubers of cei^ tain plants constitute one of the most important classes of energy-yielding foods. The potato and 46 THE NEWER KNOWLEDGE OF NUTRITION sweet potato are by far the most important rep- resentatives of this group in Europe and the Amer- icas, but several other kinds of tubers are widely used as human food in the Orient. An examination of the potato has been recently made, which reveals the special dietary properties of this tuber to be just what we should expect from its function as a storage organ for reserve food in the plant. The functions of the potato are twofold, viz., to reproduce the plant in the following generation, and to furnish a food supply for the young potato plantlet while it is developing root and leaf systems which make it independent of the food stored in the old tuber. The '^eyes" of the potato represent groups of cells which are analogous to the germ of the seed. These are the points at which the potato sprouts when the conditions are appropriate. There is underneath the skin of the potato a layer of cells which are alive and respiring during the life of the tuber, but the interior of the potato consists almost entirely of water, starch, protein, and to some extent of mineral salts. The cellular structures in the interior are gorged with starch, etc., and this portion is therefore analogous in its dietary properties with the endo- sperm of the seed. Both are comparable to a mixture of purified protein, carbohydrate, and salts, which, as we have previously seen, is not capable of support- ing hfe. This portion, hke the portion of the rice kernel, which remains after polishing, is almost lacking in both the chemically unidentified dietary DIETARY PROPERTIES OF VEGETABLES 47 essentials, fat-soluble A and water-soluble B, and accordingly cannot support life even though it may have an appropriate chemical composition as shown by analysis. The potato is to be classed wdth the seeds in its dietary properties, because it consists largely of reserve food materials and relatively little of cellular elements. The results available indicate that if the potato is steamed and the thin paperlike skin removed without the loss of the cellular layer which hes just underneath, it wdll contain relatively more of the fat-soluble A, a lack of which leads to the development of the pecuUar eye conditions pre- viously described, than do the cereal grains. Al- though it has not been subjected to experimental test, it would seem that a potato which is pared in the ordinary way and the paring discarded, is changed in its dietary properties in much the same way as is the rice kernel during the polishing process. In the latter, the germ and the bran layer are both rubbed off, lea\ing the endosperm without the small quota of cellular elements wliich it possessed in its natural state, and is correspondingly^ changed in its food value (see legend to Chart 3). The protein of the potato is not quite so valuable for growth as that of the cereal grains w^hen fed as the sole source of this dietary factor.^ There have been a number of experiments of short duration which gave results which indicate that in the human subject the nitrogen of the potato is of extraordinary value for replacing that lost tln^ough 48 THE NEWER KNOWLEDGE OF NUTRITION daily metabolism in the adult. McCoUum, Sim- monds and Parsons, have tested this question by comparing with the protein of the cereal grains the value of the nitrogen of the potato when this tuber was supplemented in such a manner as to make good all of its deficiencies except protein. The experiments involved growth tests in the young rat. The results show conclusively that potato nitrogen falls considerably below the value for growth pos- sessed by the indi\ddual cereal gi-ains, when each of these serves as the sole supply of the digestion prod- ucts of protein. The Roots Employed as Food. — The same rea- soning applies to the root crops as to the potato, with respect to the relation between dietary prop- erties and biological function. The roots which we employ as food are those which are liighly modified as storage organs, and resemble the potato in con- taining a ver}^ high water and starch content, and but very httle protein. Like the potato, there is a cel- lular layer at the periphery, and the interior is loaded with reserve food-stuffs. Appropriate feeding tests have shown that the properties of the beet resemble -those of the seed and the tuber, rather than those of the leaf.^ The fleshy roots and the potato and the sweet potato have an inorganic content which re- sembles that of the seed in a general way, so that an inspection of the anatytical data relating to the composition of the ash of the seeds, tubers and roots, gave no promise that the combination in diets of DIETARY PROPERTIES OF VEGETABLES 49 seeds with either of the latter classes of food-staffs would correct the inorganic deficiencies of the fonner. Feeduig experiments in which a seed and a tuber were combuied, and so supplemented wdth purified protein, and fat-soluble A (in butter-fat), that all the deficiencies of the mixture, except the inorganic, were made good, have shown that in the combinations of each of the more important seeds with the potato, the resulting mineral supply, which is derived solely from the natural foods themselves, is not of a char- acter suitable for the support of growth.^ The con- tent of the elements, calcium, sodium and chlorme must be augimiented by greater amounts before such food mixtures are complete with respect to their mineral content. Xo studies have as yet been made to determine the biological value of the nitrogen of the tubers other than the potato, and none at all of the edible roots. From the results of systematic feeding trials wdth mixtures of seeds alone and the same with single and multiple purified food additions, and the same t>^e of expermient using certain of the tubers and root foods in place of the seeds, it is shoTNTi that all these classes of foodstuffs resemble one another in all re- spects except in the high content of water m the tubers and roots. In the diy state they are all much like the seeds, but there is one minor difference which should be mentioned. The most miportant difference lies in the character of the nitrogenous compounds. In the seeds the nitrogen is almost all contained in 50 THE NEWER KNOWLEDGE OF NUTRITION the form of true protein. In the tubers and edible roots most of it is in the foim of much simpler com- pounds, a part being the same amino-acids which are derived from proteins on digestion. It is possible to prepare diets derived solely from vegetable products which will nourish an animal during growth and throughout life in a very satis- factory manner, but it is a surprisingly difficult task to prepare for the omnivera, an adequate diet com- posed entirely of food-stuffs of plant origin. AATiile many of the seeds contain nothing of a detrimental character, many of the leaves, when eaten, undoubt- edly do introduce into the body substances which have more or less injurious effects. The nature of these cannot be stated at the present time, but the possibility that there m.ay be an injurious effect brought about by prolonged administration of such bodies as the tannins, the glucosides and oxalic acid, certain organic bases which in some cases resemble certain of the alkaloids, and in some leaves the pres- ence of alkaloids which are highly active pharmaco- logically, can easily account for the fact that with all rations of strictly vegetable origin one would not have optimum nutrition. McCollum and Sim- mon ds have in a long Ust of trials with mixtures of leaves and seeds been unable to secure the opti- mmn of well-being in omnivorous animals. It is worthy of the greatest emphasis that in our hundreds of trials with diets derived entirely from vegetable sources, we have not succeeded in producing optimum results in DIETARY PROPERTIES OF XTGETABLES 51 the nutrition of an omnivorous animal the rat. Certain of the animals which we have restricted to foods of plant origin, have done so well that we should in the absence of much experience with diets of excellent quality, have considered them to be normal in every respect. It should be emphasized that the average performance of a group of people or animals li\'ing upon a varied diet cannot safely be assumed to repre- sent the best of which they are capable. In the study of diets the author and his colleagues have kept constantly in mind the best results we have ever seen in the nutrition of animals, as exemplified in rapidity of growth, ultimate size attained, number of young produced, and the success with which these were reared, and have attempted to assign to ever^^ experimental groujD its legitimate place on a scale of performance, which has complete failure to either grow or long remain ahve as the one extreme, and the optimum of which the animal is capable as the other. In connection with the statement which has just been made regarding the strict vegetarian diet, that it does not, so far as has been observed, induce the best results in the nutrition of the omnivora, it should be added that in human dietary practice what is generally designated as vegetarianism is in reality something veiy different. Alany people hold that they are adhering to vegetarian dietary habits, who in reality, take in addition to foods of plant origin, milk or eggs or both. This type of diet will give very 52 THE NEWER KNOWLEDGE OF NUTRITION much better results than can be secured from the use of vegetable foods alone. Lacto-vegetarianism should not be confuesd with strict vegetarianism. The former is, when the diet is properly planned, the most highly satisfactory plan which can be adopted in the nutrition of man. The latter, if strictly adhered to, is fraught with grave danger unless the diet is planned by one who has extensive and exact knowledge of the special properties of the various food-stuffs employed. CHAPTER III THE VEGETARI-IN DIET It has been pointed out in the preceding chapters that it is not possible to make a diet derived entkely from seeds or seed products, which ^ill adequately nourish an animal during growth, and it may be added that such diets will not even maintain a fully gi'own anmial in a state of health and normal physi- ological activity over a long period. Without an appropriate supplementing of seed mixtures with the elements, calcium, sodium and chlorme, no ap- preciable amount of growth has been secured with seed mixtures, in our extensive experience. It was further pointed out that the leaf is a very different thing from the seed, tuber or root, from the dietary standpoint, and these differences in nutritive prop- erties can be correlated with differences in function. The seed is a storage organ of the plant, and is filled with a reserve supply of proteins, carbohydrates, fats and mineral salts. It is in great measure non-h^ang matter, and indeed much of the contents of the seed was never a part of living matter, but only the prod- uct of it. In the leaf of the plant we have a tissue which, during life, was very active in the manifesta- tions of the properties of lining matter. With these 53 54 THE NEWER KNOWLEDGE OF NUTRITION differences in function, it was pointed out, there are found corresponding diffei^ences in the dietary values of the two types of foods, the latter being much more nearly complete foods chemically, than are the seeds, tubers and roots. Let us consider briefly the bearing of these obser- vations on the w^hole subject of human and animal nutrition. It has been pointed out that for many years the protein and energy value and its digest- ibility were assumed to determine the value of a food. The chemist is able to determine approxi- mately the amount of protein or rather its content of nitrogen which is ta,ken as a measure of the amount of protein and the fuel value of a food, and by means of experiments on animals, the extent to which a given food is digested and absorbed. He can even tell by a study of the relation between the amounts of oxygen absorbed by the tissues, and the amount of carbon dioxide given off whether the animal is burning sugar or fat in order to obtain its energy. The nitrogen eliminated in the urine serves as a meas- ure of the destruction of protein in the body. With- out in the least attempting disparagement of the value of the services of the chemist in the study of the problems of nutrition, it may truthfully be said that both his ordinary and his unusual and most searching methods for the analysis of food- stuffs fail to throw any great amount of hght on the value of a food or mixture of foods for induc- ing growth. THE \^GETARIAN DIET 55 Id addition to the cereal grains, wheat, oat, maize, rye, barley and rice, the products of the vegetable garden wliich supphed leafy vegetables, cabbage, lettuce, spinach, cauliflower, brussels sprouts, chard, celery, various '^ greens,'^ etc.; roots, such as the radish, turnip and beet; tubers, such as the potato and sweet potato, we have had available as food an abundance of meats and of dairy products. It is not strange that ^^'itll such a supply of foods it should have been taken for granted that any diet consisthig of wholesome foods, combined in such proportions and taken in such quantities as would fmnish the amounts of protein and energy wliich exper- iments on man and animals had sho\\Ti to be neces- sary under specified conditions of hving, whether at rest or at work, should prove satisfactory for the maintenance of health ua the adult and of normal gro^^i:h in the young. An appreciation of the funda- mental importance of employing proper combinations of foods, VN'as impossible, until the systematic efforts described ua the first two chapters, were made to simplify the diet as far as possible, and to derive it from restricted sources. These studies have, when the results were apphed to the haterpretation of the quahty of the diets of man in several parts of the world, revealed the fact that man is frequently faihng to make the wisest selection of food. Health and efficiency can be greatly improved by appMng the knowledge which we now possess concerning the special properties of several classes of foods, to 56 THE NEWER KNOWLEDGE OF NUTRITION the selection of the articles which shall make up the daily diet. The biological method for the analysis of single food-stuffs and mixtures of food-stuffs has made it evident that the older practice of regarding protein, energy and digestibility as the criteria of the value of a food mixture, must be replaced by a new method of presentation of the subject based upon a biological classification of the food-stuffs, the latter having its foundation in the function of the substance employed in the diet. Such a method of presentation of the subject of food values offers convincing evidence of the necessity, for the proper selection of food, that dietary reforms are greatly needed in many parts of the world. There has been much discussion of the relative merits of the vegetarian diet for man as compared with diets largely derived from vegetable foods but more or less liberally supplemented with foods of animal origin. This question has been discussed principally from the point of view of the supposed detrimental effects of a diet containing a high protein content, and the supposed beneficial effects of a sparing consmnption of protein, and from the point of view that there are sound ethical reasons why man should abstain from the use of animal foods. The adherents of the latter extreme view have never become numerous, partly because the average in- dividual has not the self-control to enable him to forego the use of meats, milk and eggs, on account THE VEGETARIAN DIET 57 of their appetizing qualities, and partly because the chances of one's succeeding in the selection of a strictly vegetarian diet which would maintain such a state of physiological well-being as would make possible the continuation of his hne are very small. Concernmg the ethical considerations involved in the eating of animal foods, nothing need be said here. The relative merits of the vegetarian as compared ^dth the mixed diet, and the evidence regarding the desirability of taking a low or high protein intake, may next receive our attention. The most elaborate attempt to test the relative merits of the strictly vegetarian diet as contrasted with the omnivorous type, was made by Slonaker.^ He fed a group of young rats on a hst of 23 vegetable foods, allowing them free choice within limits. For comparison, a similar group were fed the same foods of vegetable origin, but in addition animal food was given in moderate quantities. Since several natural foods, raw or prepared, were offered at a time, and the anim^als were allowed free choice as to what they should eat, and since no effort was made to keep track of the food consumption, or the relative amounts of the different foods eaten, the results cannot be employed for critical examination except in a limited way. The results are of the greatest interest in shomng how far instinct fails to guide an animal in the selection of its food. . Slonaker's hst of foods included nearly everything which a vegetarian in southern California would be hkely 58 THE NEWER KNOWLEDGE OF NUTRITION to have on his table during the year, and included seeds, the milhng products of seeds and leafy veg- etables, tubers and roots. The vegetarian group grew fairly well for a time, but became stunted when they reached a weight of about 60 per cent of the normal adult size. They never increased in size beyond this point. The omnivorous controls grew steadily to what may be regarded as the normal size for the adult. The vegetarians lived, on an average for the entire group, 555 days, whereas the omnivora had an average span of life of 1020 days. The vegetarian rats grew to be approximately half as large, and hved half as long as did their fellows which received animal food. Slonaker drew the conclusion that a strictly veg- etarian diet is not suitable for the nourishment of an omnivorous anim-al, but was unable to say why this should be true. The results of Slonaker were published in 1912, and just at the timx when McCollum and Davis were securing the experimental data which revealed the differences in the growth-promoting power of fats from different sources and which estabhshed the fact that a hitherto unsuspected dietary essential existed. They fed their diet of relatively pure food- stuffs described on page 16 with various fats of both anim^al and vegetable origin and found that no fat which was derived from plant tissues came in the growth-prom^oting class along with butter fat, the fats of egg yolk, and of the glandular organs. It THE VEGETARIAN DIET 59 seemed to McCollum and Davis that the most probable explanation of the results of Slonaker was the absence or shortage in his vegetarian diet of the dietary essential which is furnished so abundantly by butter fat, and which later came to be designated as fat-soluble A and to a low protein intake. With this idea in mind the^' tried during the summer of 1914 an experhnent similar to that of Slonaker 's, but modified so as to give the animals a much higher protem content than his z^ats probabl}^ took. It seemed that if Slonaker's vegetarian rats ate hberally of such leaves as cabbage and other leafy vegetables, the protein content of which in the fresh condition does not as a rule exceed 2 per cent, the content of other constituents of the diet in protein might not be high enough to give the entii^ mixture consumed, a protein content sufficiently liigh to promote growth at the optimum rate. ^IcCollum and Da\ds, therefore, fed their rats a diet which afforded them a choice among the follow- ing list of foods: wheat, maize, lye and oat kernels, cooked diy na^y beans, peas, wheat germ, corn gluten, wheat gluten, flax-seed oil m.eal, green clover, green alfalfa leaves, onions and peanuts. It vnW be observed that in this Ust there are seveial vegetable foods ha\ing unusually liigh protein contents. Corn gluten, which is a product of the com starch manufac- ture, contains about 25 per cent of protein; wheat gluten, prepared by washing gi'ound wheat free from starch, contains about 86 per cent; flax-seed oil meal, 60 THE NEWER KNOWLEDGE OF NUTRITION as much as 30 per cent, and wheat germ about 30 per cent of protein. Since animals are knowTi to grow well on many diets containing 15 to 18 per cent of protein, it seemed that with these things to select from, one possible cause of failure in Slonaker's experiments, viz., too low a protein intake, would be avoided. McCollum and Davis had not at that time discovered in the leaf the source of the dietaiy essen- tial, fat-soluble A, although it is now known that the leafy foods enable the herbivorous animal to thrive on his diet derived entirely from plant tissues. It was then assumed that when both the leaves and so many different seeds as well as the germ was supplied there could be little doubt that everything which a herbivorous animal requires was present in the foods supplied. The rats fed this wide variety of vegetable foods, and with a most liberal supply of protein, duplicated in all respects the results which Slonaker had de- scribed. They grew at about half the normal rate for the first few weeks, then became permanently stunted, none ever reaching a size much greater than half that of the average normal adult. The addition of butter fat to the diet of some of these animals failed to benefit them in any noticeable degree. The answer to the question as to why rats do not thrive on such strictly vegetarian food mixtures was not secured from these experiments. It was, however, soon after learned wherein lay the cause of failure of animals so fed. THE VEGETARIAN DIET 61 McCollum, Simmonds and Pitz, began in 1915 a series of feeding experiments in which the diets of rats were derived solely from a mixture of one seed and one diy leaf.- In marked contrast to the failure of animals to grow on any mixtures of seeds it was found that in many cases a mixture of a seed with a leaf formed a diet on which considerable growth could be secured. Even polished rice, which as has been already described, requires four types of supplementing, \dz, protein, mineral salts, fat- soluble A and water-soluble B, before it becomes dietetically complete, was found to induce fairly good growth when fed with ground alfalfa leaves in the proportion of 60 per cent of the former to 40 per cent of the latter. On this simple monotonous mix- ture, young rats grew from w^eaning time to 83 per cent of the normal adult «"ze, and one female even produced two Utters of young, both of ^vhich w^ere, however, allowed to die within a few^ days. A mix- ture of rolled oats, 60 per cent, and alfalfa leaves, 40 per cent, ground together makes a Yery much better diet. On this simple mixture young rats have been observed to grow to the normal adult size, and to reproduce and rear young. One female reared fourteen out of seventeen young born in three litters. INIaize and alfalfa leaf, wheat and alfalfa leaf, are not so satisfactory^ for the production of growth as is a mixture of rolled oats and alfalfa leaves. INIix- tures of the latter leaf with legume seeds, peas and beans, give still poorer results. (Chart 6.) These 62 THE NEWER KNOWLEDGE OF NUTRITION results made it evident that there is nothing in vegetarianism per se, which makes it impossible to nourish an omnivorous animal in a satisfactory manner. It is only necessary to make a proper selec- tion of food-stuffs, and to combine them in the right proportions. In all the experiments described, in which the diet was made up of so simple a mixture as one leaf and one seed, they had not obtained the optimum of growth, reproduction or rearing of young. It seemed probable that the reason why they did not more closely approximate the optimum in the nutrition of animals restricted to a cereal grain and a leaf, might He in too low a protein mixture, or a protein mixture which was not of very high bio- logical value. In 1915, McCollum, Simmonds and Pitz ^ fed a group of young rats on a monotonous mixture consisting of maize 50 per cent, alfalfa leaf (dry) 30 per cent, and cooked (dried) peas, sub- sequently dried, 20 per cent. The three ingT-edients were ground together so finely that they could not be picked out and eaten separately. This diet in- duced growl h at approximately the normal rate and the production and rearing of a considerable number of young. The young grew up to the fuU adult size and were successful in the rearing of their offspring. Without ever tasting anything other than this mo- notonous food mixture, as their sole source of nutri- ment after the weaning peiuod, this family of rats remained nearly normal, and successfully weaned the THE VEGETARIAN DIET 63 young of the fourth generation, with no apparent diminution in vitahty. At this point the experiment was discontinued. The failure of Slonaker's rats to thrive on the vegetarian diet is to be explained on the basis of several faults. In the first place, the diet was of such a nature that the animals could hardly do other- wise than take a rather low protein intake. Sec- ondly, the leaves, which foimed the only constituents of the food supply which contained enough mineral elements to support growth, were fed in the fresh condition. In tliis form the water content and bulk is so great that it would be practically impossible for an animal whose digestive apparatus is no more capacious tlian that of an omnivora, to eat a sufficient amount of leaf to correct the inorganic deficiencies of the rest of the mixture, which consisted of grains, seeds, tubers, and root foods. The same physical limitations would hkewise determine that the animals would fail to secure enough of the fat-soluble A to supplement the deficiency of all the ingredients of their diet other than the leaves in respect to this factor. This would not form so important a fault as the inorganic deficiencies, but would be an im- portant depressing factor. Thirdly, success or failure would turn in great measure on the extent to which the animals would be guided by instinct in the selection of the proportions of the several types of food-stuffs which was offered them. In the opin- ion of the author the appetite is by no means so 64 THE NEWER KNOWLEDGE OF NUTRITION safe a guide for the proper selection of foods as has generally been supposed. From the results of the experiments just de- scribed it was necessary to conclude that the leaf differs from the seed in that it contains in satis- factory amounts the dietary factors which are found in the seeds in too small amounts. These include the three inorganic elements, calcium, sodium and chlo- rine, the fat-soluble A and a protein supply which supplements at least in some degree the proteins of the seed. These, it will be remembered, are the three and only purified food factors which need be added to each of the seeds singly in order to make it dietetically complete. It is therefore, possible to de- vise a diet which is deiived entirely from vegetable materials which will produce normal growth and the optimum physiological well-being. At the Iowa Experiment Station, Ewaid ^ has con- ducted extensive experiments of a character which were intended to demonstrate that the appetite and instincts of the hog serve to enable it to make such an adjustment of the relative amounts of the several food-stuffs offered it, as may induce better results in the rate of growth than can be generally secured when the adjustment is made by the feeder, and the mixture of the ingi^edients of the ration are offered in a form w^hich admitted of no choice by the animal. The data secured in many trials seem to show that there is some basis for the belief that this element of selection by the animal itself is worth taking ad- THE VEGETARIAN DIET 65 vantage of. It should be mentioned that, as a rule, m all these trials the animals were given a choice of only three foods, one of these being a cereal grain, another, a protein-rich food and a tliird a plant leaf. In some experiments a salt mixtm^e was made avail- able. The reasons for the employment of the leaf as a never failing constituent of the food supply of the growing pig could not have been explained be- fore the studies of IMcCollum and his co-workers, with simplified diets and with diets restricted as to source to a single food-stuff, and until the latter had been fed with single and multiple food additions to ascertain the exact nature of the dietary faults of each. In connection with the types of diets em- ployed by E\^"ard it should be mentioned that in case the animal ate fairly liberally of all the food- stuffs offered him, a sei^ious mistake would be hardly made, since the proportions of the several con- stituents eaten could be varied to a considerable de- gree and giowth still take place. In the case of the mixture of maize 50 per cent, alfalfa leaves 30 and peas 20, described above (Chart 7) it has been found that for the rat these are the best proportions in which these three ingredients can be mixed for the promotion of growth and reproduction. It has been further established that using these three food-stuffs, a moderate amount of growth may be secured, but few, if any, young will ever be produced if the mix- ture fed contains more than 50 per cent or less than 20 per cent of alfalfa leaf. The importance of com- 66 THE NEWER KNOWLEDGE OF NUTRITION bining the natural foods in the right proportions is easily seen from these results. It is interesting to note further, that shifting the proportions of maize, peas and leaf in this mixture over a range of 20 per cent does not materially change the protein content, or indeed, the chemical composition of the food mix- ture in any way, to a degree that could be expected to make so great a difference in the state of nutrition of the animals as is actually observed. There are now available the results of a very ex- tensive series of feeding trials in which the rations were made up of one seed, one leaf and one legmne (pea, bean) in various proportions. These have failed to reveal any mixture which is quite the equal of the first ration of this type ever employed, viz., that composed of maize 50, alfalfa leaf 30 and peas 20 per cent. It is, of course, easily possible that better mixtures of vegetable foods may be found by further search, but these results show very definitely that for the omnivorous ty^e of animal, whose digestive tract is so constituted that the consumption of large volum.es of leafy foods is not possible, it is by no means a simple matter, if indeed possible, to derive the diet entirely from the vegetable foods, and se- cure the optimum of well-being. The data afforded by the experiments described form a demonstration of the fact that wide variety is of httle value as a safeguard to nutrition. Chemical analysis, no matter how thorough, fails to throw much hght upon the dietar>^ value of a food-stuff. The only way in which THE VEGETARIAN DIET 67 the problems of nutrition can be solved is through numerous properly planned feeding experiments, but such studies were not possible before the solution of the problem of successfully feeding mixtures of purified food-stuffs. These studies led to the formula- tion of an adequate working hypothesis regarding what factors operate to make an adequate diet, and m.ade possible the interpretation of the cause of success or of failure with diets of the complexity em- ployed in daily life. It will be shown later that the consumiption of milk and its products forms the great- est factor for the protection of mankind, in correcting the faults in his otherwise vegetarian and meat diet. The fact, that although the cereal grains each con- tain every inorganic element which is contained in an animal body, and every one which is a necessary constituent of the diet, but in too small amounts in the case of three of them, to enable the animals to grow, revealed the mineral constituents of the diet in a new and imxportant light. The animal is sensi- tive to either the actual amounts of certain of the mineral elements in the food mixture, or to the re- lationships among them. Sidney Ringer was led in 1891 to his description of Ringer's solution, as the result of the observations in physiolog;^^ that muscle behaves more nearly normally in solutions con- taining certain salts in definite proportions. Ringer's solution contains, for each 100 molecules of sodium chloride, two molecules of calcium chloride and two to one molecules of potassium chloride, together with 68 THE NEWER KNOWLEDGE OF NUTRITION a trace of a magnesium salt. Loeb,'' Howell ^ and others had described many experiments showing the profound effects upon the subsequent development of the eggs of vaiying in certain ways the composition of the salt solutions in which unfertilized eggs of certain marine animals were kept. In this way the earliest stages of development which are ordinarily observed only in the fertilized egg, could be caused to take place in eggs into which no sperm had en- tered. In the nutrition of the higher animals, it had never been made clear how dependent the organism is on the rate at which the blood stream receives mineral nutiient. The fact that the cereal grains are too low in three inorganic elements to admit of growth, made it clear that food packages just as they come from the hand of Nature, are not necessarily so constituted as to promote health. CHAPTER IV THE FOODS OF ANIMAL ORIGIN It is well knowTi from common observation that milk, when it serves as the sole food of the infant, serves to keep it groT\T.ng normally and in good health over a long period. There has occasionally arisen a discussion as to whether milk is a suitable food for the adult, and as to whether it is the ^^deal" food. ]\lilk:, hke the cereal grains and most other natural foods, contains all the essential food elements, and human experience teaches us that the proportions in which they occur in this product are much more satisfactory than in many other natural foods. An- nuals gi'ow well on milk, but it is not easy to find even complex food mixtures of vegetable foods which will support optunum nutrition in the omnivora during gi'owth. ]Milk is deficient in iron, as is shoTvn by chemical analysis. It has long been known that there is de- posited in the spleen of the new-born animal a reserv^e supply of iron, which ordinarily suffices to tide it over the suckhng period. Ordinary drinking water almost always contains small amounts of non, and tliis doubtless aids in some degree m preventing iron starvation in the infant. 69 70 THE NEWER KNOWLEDGE OF NUTRITION That milk is a complete food, capable of supplying all the nutrients necessary for the prolonged main- tenance of growth, health and the ability to produce and rear young, was shown by an experiment con- ducted by the author at the Wisconsin Experiment Station. A female pig was removed from its mother, which was still nursing it at the weight of 17 pounds. She had doubtless eaten of the mother's ration to some extent but her principle food had been her mother's milk. After rem.oval from the mother, this pig was confiDed in a pen ha\dng a board floor, and was fed nothing but milk during a period of 17 months. During the first few months only whole milk w^as fed, but later it was necessary to replace this in part by skim milk. The animal weighed 406 pounds at the age of thirteen months. At this age she produced eight living and two dead pigs, and successfully brought the young to an average weight of seventeen pounds. She had access to wood shav- ings, and ate some of them. There can be no doubt that the milk which she consumed was enriched to some extent with iron by being in contact with cans having part of the surface free from tin. City drink- ing water was also furnished and this contained appreciable amounts of iron. The animal must have been able to conserve its hmited iron supply in a ver>^ efficient manner. Milk is, therefore, capable of nourishing the pig during many months, wdth no other modification or additions than small amounts of iron. That it is THE FOODS OF ANIi\L\L ORIGIN 71 best to select milk as a monotonous and restricted diet during adult life, no one familiar with the prin- ciples of nutrition would maintain. Milk is, however, without doubt our most important food-stuff. This is true, because the composition of milk is such that when used in combination with other food-stuffs of either animal or vegetable origin, it corrects their dietary deficiencies. Combinations of equal weights of milk and one of the cereal gi^ains give excellent results m the nutrition of animals during gi^owth, and grain mixtures supplemented \\dth milk support well in adult life the function of reproduction and rearing of 3^oung. This is because of the excellent quality of its proteins, the peculiar composition of its in- organic content and the remarkable content of the dietary essential, fat-soluble A, in the fats of milk. Milk, hke nearly all of the other natui^al foods, con- tains a great abundance of the second dietary essen- tial of unknown chemical nature, water-soluble B. The extraordinaiy value of the proteins of milk has been abundantly demonstrated by experiment. ]\IcCollmn ^ conducted a series of expermients with growing pigs to determme the extent to which they could retain the protein of the food for the construc- tion of new body protem. The pig was selected be- cause it is necessaiy in such studies to work ^^'ith an animal whose growth mipulse is as great as pos- sible. Only with such species is it to be expected that the animal \\\\\ utilize the proteins for gi'owth to the maximum extent made possible by the chem- 72 THE NEWER KNOWLEDGE OF NUTRITION ical character of the food protein. The human infant has but httle growth hnpulse because its period of infancy is long and the adult size not great as compared with the size at birth. A comparison of the human infant with the rat and the young pig (swine) in their capacity to grow in early life is of interest. The human infant weighs not far from seven pounds at birth, and during the first year of life is ordinarily able to multiply its initial body weight by three, for the average weight at one year is about twenty-one pounds. We may feed it human milk the entire time, or unmodified cows' milk during the greater part of the year, without in any important degree modifying its rate of growth. In the latter case, we should be supplying it with perhaps double the amount of protein that it would receive were it fed human milk, since the latter contains on an aver- age about 1.6 per cent and the former about 3.5 per cent of protein. In marked contrast to the feeble capacity of the human infant to store new tissue and increase in size, stand the rat and the pig. The rat at birth weighs about 4.83 grams, and contains about 0.064 grams of nitrogen. At 280 days of age the male should weigh about 280 gi^ams, and if moderately fat will contain about 8.5 grams of nitrogen. The rat is able, therefore, in a period of 280 days to multiply its initial body weight by about 55, and its initial body nitrogen content (protein) by 133. THE FOODS OF ANIMAL ORIGIN 73 The newborn pig weighing two pounds will con- tain about 134 grams of dry matter and 11.9 gi-ams of nitrogen. In 280 days it may, if properly fed, reach a weight of 300 pounds. It would then have a nitrogen content of not less than 2407 grams. These changes in size entail a multiplication of the initial body weight by 150 and of the initial body nitrogen content by 202. The farm pig is ap- parently the most rapidly growing species of land animals. Such considerations determined the selection of the pig as a subject for the test of the biological value of the proteins of the various natural food-stuffs. The plan involved keeping the animal for a period of several days on a diet free from protein, but con- taining sufficient starch to cover the energy require- ments. WTien the nitrogen elimination in the urine reached a constant low level which represented the irreducible minimum, resulting from the ''wear and tear" of the tissues, the animal was fed a diet con- taining protein derived solely from a single grain, or other single food-stuff. A record was kept of the intake of the element nitrogen, and of the daily loss of this element through the excreta, and from these records the percentage retained for growth was ob- tained. Similar experiments were carried out using milk as the sole source of protein. The following table smnmaiizes the results obtained. 74 THE NE^^^ER KNOWLEDGE OF NUTRITION Per Cent of Ingested Protein Retained for Growth by THE Pig Per cent of ingested Source of protein protein retained Corn 20.0 Wheat 23.0 Oats (rolled) 26.0 Milk 63.0 The figures in the table are averages of a consider- able number of results and represent the general trend of the data. The experimental periods varied from 30 to 60 days. There can be no doubt that the proteins of milk are far superior to those of any foods derived from vegetable sources. The problem of determining the relative values of the proteins of the different foods when fed singly, sup- plemented with purified food additions that their diet- ary deficiencies were made good, was approached in a different way by McCoUum and Simmonds.^ Rats were fed diets in which the protein was all furnished by a single natural food-stuff, but the plane of protein intake was varied from very low to higher intakes, in Older to determine what was the lowest per cent of protein in the food mixture which would just suffice to maintain an animal without loss of body weight. The rations consisted of the following substances: Seed Amount to give the protein intake desired Growth-promoting fat (butter-fat) 5.0 per cent Suitably constituted salt mixtures 3 to 5 per cent Agar-agar (to furnish indigestible matter) 2.0 per cent Dextrin To make 100 per cent. THE FOODS OF ANIMAL ORIGIN 75 The results showed that there are indeed very great differences in the amounts of protein from different seeds, which are necessary to maintain an animal without loss of body weight. The results for the more important seeds used as human foods are summarized in the follomng table. Table SH0\\^XG the Lowtest Plane of Protein Intake De- rived FROM A Single Seed Which Just Suffices to ]\Iain- TAiN AN A171MAL in Body Weight, when the Factors Other than Protein are Properly Constituted Source of Protein Plane of Protein Necessary for Maintenance Milk 3.0 per cent of food mixture ^ Oat (rolled) 4.5 " " '' " Millet seed 4.5 '^ " " '' Maize 6.0 '' '' " " Wheat 6.0 " " " " Polished rice 6.0 " " " " Flaxseed 8.0 " " " '' Na^ybean 12.0" " " '' Pea 12.0 " " '' " These maintenance experiments were of three to six months' duration. The data obtained with the pig is seen to be in harmony in a general way with those obtained with the rat, and help to substantiate the view which is supported by all the evidence available, viz: that from the chemical standpoint, the dietaiy require- ments of one species of animal are the same as those of another. That there are great differences in the physical characters of the diet which suffice for, 76 THE NEWER KNOWLEDGE OF NUTRITION or are required by certain species as contrasted with others, is a matter of common observation. The ruminants actually require coarse herbage as a part of their food, in order that the aUmentary tract may function properly, whereas such physical properties in the diet of the omnivora are wholly out of place beyond very limited amounts. In considering the value of milk as a constituent of the diet it should be borne in mind that with respect to the protein factor it may enhance tne value of the proteins of the remainder of the food. It may supply in relative abundance those amino-acids which are present in such smaU amounts that they form the first, second, etc., limiting factors in determining the value of the protein for growth or maintenance, as well as by the direct addition to the food mixture, of the intrinsically good proteins of the milk. When taken as the sole food supply by the adult, milk is very liable to produce constipation and be- cause of its high protein content, may lead to the ex- cessive development of putrefactive bacteria in the intestine. The cages of rats fed solely on milk de- velop an offensive odor. The addition of carbohy- drate, such as starch or certain of the sugars, tend to cause the disappearance of the obnoxious flora from the alimentary tract, and the development, instead, of types which do not produce injurious decomposi- tion products in their action on proteins. Meats. — The muscle tissue of an animal con- sists of highly specialized tissue whose chief function THE FOODS OF ANIMAL ORIGIN 77 is to produce mechanical work through contraction. It is in addition a storage organ in which glycogen, a form of starch, and also fats are stored as reserve foods. It contains but httle of cellular structures in the sense that the glandular organs, such as the liver, kidney, pancreas, etc, do. Chemical analysis shows the muscle to consist, aside from the reserve food-stuffs, prmcipally of water, protein and salts. The glandular organs yield a high content of nucleic acid, while the muscle tissue yields but little in pro- portion to its weight. The inorganic content of the muscle tissue resembles that of the seed of the plant, rather than the leaf both in amount and in the rel- ative proportions among the elements. Corresponding with the specialized function, and the peculiarities in composition just mentioned, we find that its dietary properties are comparable with the seed rather than the leaf. In fact, muscle tissue differs markedly from the seed in only one respect, when considered as a food-stuff, viz., in the quality of its proteins. These are distinctly better than those of the seeds with which investigations have been conducted. The inorganic content must be supplemented by the sam.e inorganic additions as the seed, and the muscle proves to be relatively poor in its content of the unidentified dietary essential fat-soluble A, as compared with such foods as milk, egg yolk and the leaves of plants. Smce the inorganic part of muscle resembles that of the seed, except that the latter is poorer in iron 78 THE NEWER KNOWLEDGE OF NUTRITION and it is low in its content of fat-soluble A, it does not supplement the seeds in an appreciable degree other than with respect to the protein factor. It follows, therefore, that we should not expect to se- cure growth and normal nutrition with mixtures of seeds, and meat and experimental trials demonstrate that this is the case. Mixtures of meat (muscle) and seeds require to be supplemented with respect to sodium, calcium and chlorine, just as do seed mix- tures alone^. The fat-soluble A content of such iiiLxtures, unless millet seed is one of the seeds pres- ent to the extent of 25 per cent, must be increased by suitable additions before the optimum nutrition can be attained, and the animals can successfully bear the strain of reproduction and lactation. Meats are, therefore, but partial supplementary foods when employed w^ith the seeds or the products prepared from seeds, such as wheat flour, corn meal, polished rice, etc. Such diets can be partially corrected by the liberal use of leafy vegetables, but better by the use of the latter along wdth milk. The pronounced deficiencies of m.uscle tissue as a food-stuff, naturally suggests the question of the reason for the success of the nutrition of the strictly carnivorous animals. The explanation is found in the order in which such creatures select the parts of the carcasses of their prey. The larger carnivorse, after striking down an animal, immediately open the large veins of the neck and suck blood as long as it flows. Their second choice of tissues is the Uver, and THE FOODS OF ANIMAL ORIGIN 79 following this the other glandular organs. Muscle tissue is only eaten aftez' these have been consumed. With such a selection the animal secures eveiything which it needs for its nutrition except a sufficient amount of calcium, and this is obtained througli gnawing off the softer parts of the extremities of the bones. The failure of many carnivora to thrive w^hen confined in zoos, it probably the result of their being fed too largely upon muscle tissue and bones. They should be supplied with an abundance of the gland- ular organs and with blood to make then diet com- plete. With rats McCollum, Simmonds and Parsons have observ^ed fairly satisfactory grow^th on equal parts of muscle tissue (round steak) and dried blood, whereas either of these alone cannot induce growth.^ The Glandular Organs. — The liver and kidney may serve as typical examples of the glandular or- gans which are employed as foods. There are cer- tain organs of internal secretion, such as the thy- roid, and suprarenal glands w^hich elaborate products w^hich are highly active pharmacological agents, and the liberal use of these glands as food would lead to disastrous consequences. The glands contain but lit- tle of the inorganic elements in which the seeds are deficient. Their proteins are probably of excellent quality, but have not yet been carefully investigated. The glands consist largely of actively functioning cells, having specialized functions, and accordingly they prove to contain a more liberal amount of both 80 THE NKWER KNOWLEDGE OF NUTRITION the fat-soluble A and water-soluble B than does the muscle. In respect to the former of the unidentified dietary essentials the glandular organs surpass the seeds in value/ From this description it will be seen that the glandular organs approximate more closely complete foods than does the muscle, but it is likewise apparent that these tissues do not form efficient supplements for the seeds and their products. Eggs. — The egg contains all the chemical com- plexes necessaiy for the formation of the chick dur- ing incubation. The egg is therefore to be expected to furnish everything which is needed for the nutri- tion of a mammal, for as has been already stated, the evidence all supports the beUef that the chemical requirements of one species are the same as another. The egg is indeed a complete food, but not one which produces the optimum results when employed as the sole source of nutriment. Aside from the calcium content of the white and yolk of the egg, which is much lower than that of milk, the contents of the egg resemble milk in a general way in nutritional value. The high content of milk sugar in the latter, and the almost complete absence of carbohydrate from the egg, cause them to differ considerably in the physi- ological results which they produce on animals when each is fed as the sole source of nutriment. Egg, when fed alone, encourages much more than milk the development of putrefactive organisms in the aUmentary tract. The shell of the egg consists THE FOODS OF AXHIAL ORIGIN 81 principally of calcium carbonate, and during in- cubation this is to some extent dissolved and ab- sorbed for the formation of the chick. AYhen eggs serve as human food the shells are discarded. There are distinct differences in the chemical natm-es of the constituents of eggs as contrasted with milk. The principal protem of egg yolk, like that of milk, contains phosphorus, but the fats of milk are phos- phorus free, whereas phosphorized fats (e. g., leci- thins) are very abundant in egg fats. There is an abundance of lactose in milk, whereas the egg con- tains but a trace of sugar. These differences have Kttle, if any, diefcar>^ significance. The yolk is es- pecially rich in both the fat-soluble A and water- soluble B. With the exception of milk the foods of animal origin do not supplement completely the diet- ary deficiencies of the seeds and their products. We are now able to make certain generalizations of fundamental miportance regarding the t^-pes of combinations of the natural food-stuffs which may be expected to give good results m the nutrition of an annual . (1) Seed mixtures, no matter how complex, or from w^hat seeds they are derived, ^^'ill never induce optimum nutrition. Seeds with tubers, or seeds with tubers, roots and meat (muscle) ^^ill in all cases fail to even approxi- mate the optimum in the nutrition of an animal during growth. (2) The only successful combinations of natural 82 THE NEWER KNOWLEDGE OF NUTRITION foods or milled products for the nutrition of an ani- mal are: (a) Combinations of seeds, or other milled products, tubers and roots, either singly or collectively taken with suf- ficient amounts of the leaves of plants. (b) Combinations of the food-stuffs enu- merated under (a) taken along with a sufficient amount of milk to make good their deficiencies. Milk and the leaves of plant are to he regarded as protective foods and should never he omitted from the diet. Milk is a hetter protective food than are the leaves, when used in appropriate amounts. It should be appreciated that not all diets which conform to the requirements laid dowTi in the above generalizations, will give equally good results. This is especially true of diets of the type under (2). Chart 6 shows the great differences in the food values of a few mixtures of seeds and leaves. It can be stated definitely, however, that diets which are not made up according to the second plan, will never be satisfactory. CHAPTER V THE DISEASES REFERABLE TO FAULTY DIET, OR THE SO-CALLED '^DEFICIENCY DISEASES" It has been pointed out that in the year 1911 Funk took up the study of the disease beri-beri. He made use of the observation of Eijkman, that the symp- toms could be produced expermientally in birds by feeding them exclusively upon polished rice for two to four weeks, whereas birds remain for much longer periods in a state of health when fed exclusively upon the unpohshed grain. He also made use of the ob- servation of Fraser and Stanton, that an alcohoUc extract of rice polishings would effect a ''cure" of pol^^ieuritic birds. Funk made nmnerous elaborate and painstaking attempts to separate the "curative" substance, and wrote extensively on what he believed to be "deficiency" diseases. Under this term he included beri-beri, scur^T) pellagra and rickets. Hopkins discovered that small additions of milk to food mixtures composed of purified protein, carbohydrate, fats and inorganic salts, rendered them capable of inducing growth, whereas without such additions no growth could be secured. The effects were out of all proportion to the energ^^, or protein value of the added milk, and he suggested the exist- 83 84 THE NEWER KNOWLEDGE OF NUTRITION ence of '' accessory" food-stuffs, which are required in but small amounts, and which are absent from the mixtures of purified food-stuffs, which fail to promote growth. To the supposed '^curative" substances, the presence of which in the diet prevents the develop- ment of several syndromes enumez^ated. Funk gave the collective name ^Sdtamines." Thus he distin- guished an antineuritic ^^vitamine," an antiscorbutic 'Sdtamine," etc. These supposed substances have since been variously designated as '^growth sub- stances," ^^ growth determinants," ^^food hormones," ''accessory" food substances, etc. McCollum and Davis through their studies wdth diets of purified food-stuffs, pointed out that it was highly probable that there are essential in the diet but two substances rather than groups of substances of imknoTVTL chemical nature, and it was sho\\Ti, as has been pointed out, that one of them is associated with certain fats, while the other is never found with the isolated fats of either animal or vegetable origin. McCollum and Kennedy ^ suggested that they be provisionally called fat-soluble A and water-soluble B, because of their characteristic solubihty in fats and in water respectively. The above terms, except the last two, are mis- nomers. The word accessory, carries the idea that the substances in question are dispensable. Con- diments may be desirable, but they can be dispensed with, and are properly designated as accessory food substances. An indispensable food complex cannot ''DEFICIENCY" DISEASES 85 properly be designated by this term. ^^Vitamine" is objectionable, because the prefix vita connotes an importance of these dietary essentials greater than other equally indispensable constituents of the diet, such as certain of the amino-acids which play a role in protein metaboUsm. The ending amine has a definite and specific meaning in organic chemistry, being used to designate a compoimd derived from ammonia by the substitution of one or more of its h^^drogen atoms by various organic radicals. Any substance to be properly designated as amine must contain the element nitrogen. There is no e\ddence that either of these unidentified dietary essentials is an amine, and indeed fat-soluble A probably con- tains no nitrogen, for it is especially abundant in butter fat, and the latter is practically free fix)m this element. ^'Food hormones" is an objectionable term, be- cause all the evidence available indicates that both the fat-soluble A and water-soluble B are never- faihng constituents of the cells of both annual and plant tissues. They have nothing in common with the hormones. The latter are chemical substances which are formed in the body by special tissues and contributed to the blood stream where they cause the stimulation of certain other tissues to physiolog- ical activity. They are chemical messengers, wliile the substances under discussion are food complexes, apparently necessary for all the living cells of the body. It has been pointed out that the content of 86 THE NEWER KNOWLEDGE OF NUTRITION both of these two dietao' essentials appears to rim parallel to the content of cellular elements m the food-stuffs, regardless of their source. '^Growth substances" and '^ growth determinants" are not good terms for the reason that the substances in question are just as essential for the maintenance of a full grown animal in a state of health as they are for the support of growth in the young. Further- more, in actual experience, rations are found in which the content of one or more essential amino- acids are present in such amounts that they form the limiting factor which determines the value of the ration . It is easy to prepare a food mixture in which any one of the eight or nine essential inorganic elements which the diet must furnish, wdll be so low as to prevent the growth of an animal even though the food is otherwise of satisfactory character. In one case the addition of a suitable sodium compound or in another a calcium or a potassium salt might induce growth, and these elements might, with just as much propriety, be called ^'growth determinants" as to apply this telm to one of the still unidentified food essentials. The term might fittingly be appHed to any of the indispensable components of the diet, such as certain of the amino-acids, which result from the digestion of the proteins. All natural food-stuffs, such as the seeds of plants, the leafy vegetables, fruits, roots, tubers, meats, eggs and milk, contain certain amounts of all the substances which are indispensable components of "DEFICIENCY" DISEASES 87 the diet. There is, however, great variation in the quality of the different foods with respect to the sev- eral factors. Some contain much protein, others httle, and a similar variation mth respect to other constituents is found. The special properties of the several groups of food-stuffs have been described in Chapters III and IV. The best sources of fat-soluble A are whole milk, butter fat and egg yolk fats and the leaves of plants. The seeds of plants contain less and those products derived from the endosperm of the seed are very poor in this substance. Such food-stuffs as bolted flour, degerniinated corn meal, polished rice, starch, glucose and the sugars from milk, cane, and beet are practically free fx^om the fat-soluble A. The specific result of a lack of a sufficient amount of this sub- stance in the diet is the development of a condition of the eyes which appears to be rightly classed as a tr^-pe of xerophthabiiia. The eyes become swollen so badly that they are opened with difficulty or not at all. The cornea becomes inflamed, and unless the missing dietary essential is supplied, blindness speedily results. Osborne and Alendel ^ have also noted this condition in exi^erimental animals and its relief by feeding butter fat. The introduction into the diet of 5 or more per cent of butter fat will cause prompt recovery in cases w^here the an- imals are within a few days of death. Complete re- covery takes place within two weeks if the sight has not been destroyed. The normal condition of the 88 THE NEWER KNOWLEDGE OF NUTRITION eyelids can be restored even after the sight is gone and the cornea has faded. WTien the diet consists principally of one of the cereal grains such as the wheat, oat or corn kernel, or even a mixture of these, and it is satisfactorily supplemented with respect to the inorganic elements in which they are deficient, viz., calcium, sodium and chlorine, and their proteins are enhanced in value by the addition of a protein of good quality, animals restricted to such a food supply may long escape the onset of this disease. The seeds are not entirely lacking in the substance, fat-soluble A. They contain, especially the wheat and corn kernels, about half the amount required to maintain an animal in a state of health. If the seeds or their mixtures are supplemented with respect to but a single dietary factor, e. g. inorganic salts, but the protein content is left of relatively low biological value, the debilitating effects of the low value of the food mixture in the two dietary factors (protein and fat-soluble A) simultaneously will hasten the onset of xerophthalmia.^ When judging the effects of the diet on an animal, it is necessary to take into account the fact that the diet is a complex thing, and that if it is properly constituted with respect to all factors but one an animal may tolerate it without apparent injury whether the fault lies in one or another of the essential components. The value of one component m^ay fall well below that which will lead to serious mal- nutrition, when a second dietary factor is likev/ise poor. "DEFICIENCY" DISEASES 89 The idea should not be entertained that butter fat is the only food which supplies the fat-soluble A. If the diet contains a liberal amount of milk, eggs, glandular organs or the leaves of plants, it wdU, if otherwise satisfactorily constituted, prevent the onset of the eye disease. The seeds and seed prod- ucts, such as wheat flour (bolted), degerminated corn meal, polished rice, starch, the sugars, s>Tups, tubers, roots, such as the radish, beet, carrot, tui-nip, etc., and also the muscle tissue of animals, such as ham, steak, chops, etc., do not contain enough of the fat-soluble A to be classed as important somxes of this dietary essential. The tubers and roots appear to be somewhat richer in it than ai-e the seeds. '^ In the form in which they are ordinai^ily eaten, as mashed or baked potato, baked sweet potato, fresh or creamed radish, cooked carrots, beets or creamed turnips, the water content of the dish as served is so high that the amount of soUds eaten is not a very high per cent of the total food supply, and the protective action is correspondingly limited. In America, however, potatoes are seldom eaten without the addition of butter. The vegetable fats and oils such as olive oil, cottonseed oil, peanut and cocoanut oils, although good energy yielding foods, do not furnish this dietary essential. The body fats of animals such as lard, beef fat, etc., are not important sources of the fat-soluble A. McCollum and his co-w^orkers have repeatedly observed in experimental animals the type of xeroph- 90 THE NEWER KNOWLEDGE OF NUTRITION thalmia of dietary origin which has been described above. They have many times rescued animals from the thi^eshold of death by the addition of butter fat to the diets of the animals which were suffering from the disease which was brought about by a lack of a sufficient amount of the fat-soluble A in their food. It is important to inquire whether or not this disease has ever occurred in man. It is not easy to decide from the descriptions, in the clin- ical literature, of the eye troubles of poorly nourished peoples in various parts of the world, which are of the peculiar tyipe w^ith which we are now dealing, and which are due to other causes. Soreness of the eyes is common among many primitive peoples. Herdlika ^ describes severe eye troubles among the American Indians of the southwest, and attributed them to too great exposure to strong sunlight. In- fection of the eyes is common among many peoples, and the clinician, not being aware of the existence of a pathological condition of the eyes due to faulty diet, would, of course, be inclined to attribute such conditions to other causes. There are several instances of the occurrence of conditions described in the Uterature as xerophthal- mia, which seem to be beyond question, cases in which the disease has occurred in man as the result of specific starvation for the dietary^ essential, fat- soluble A. Mori ^ in Japan described in 1904, four- teen hundred cases of xerophthalmia among children in a time of food shortage. He describes the condi- ■ .22 .2 ^ S o .22 ^ k-^ ^^ L^ /— \ 3 C3 43 bO ^ O bC 5l o fl "DEFICIENCY" DISEASES 91 tion in a manner which agrees closely with that which McCollmn and Sininioiids have observed in animals whose diets were lacking in a sufficient amount of fat-soluble A. The eAddence that he was dealing with this disease is made almost conclusive by the fact tliat he states that feedmg chicken livers effected a cure. It has been alx'eady mentioned that the glandular organs contain the fat-soluble A in fanly liberal amounts. The Japanese have, as a rule, no dairy products. Their diet consists of seeds and seed products, roots, tubers, leaves and meats, prin- cipally fish. Their principal sources of the dietaiy factor in question are the leafy vegetable and eggs, the former of which in normal times they consume much larger amounts than do the peoples of most j^arts of Europe and America. Shortage of food will occur usually owing to drought, and the first products which fail are the green vegetables, and accordingly the dietary essential which would be least abundant would be the fat-soluble A. ]\Iori attributed the xerophthahnia to fat starvation. It seems highly probable, how^ever, that a lack of fat w^as not in it- self the cause of the disease, but rather the lack of the unidentified dietary essential which is associated with certain fats, but is not furnished by any of the isolated fats of vegetable origin, although it is present in plant tissues where these contam cellular struc- tures. Mori states that the disease does not occur among fisher folk. Bloch ' has recently described forty cases of severe 92 THE NEWER KNOWLEDGE OF NUTRITION necrosis of the cornea with ulceration, in the vicinity of Copenhagen. The children had been fed nearly fat-free separator skim niilk, and were atrophic or dystrophic and anemic. He attributed the disorder to fat starvation, since the children responded with recovery when fed breast milk, or in the case of older ones, with whole milk mixtures and to codliver oil administration. The recovery, it will be noted, followed the feeding of those substances which are good sources of the fat-soluble A. Czerny and Keller ^ describe a similar condition of the eyes in children suffering from malnutrition as the result of being restricted to a cereal diet. It seems certain that these cases of xerophthalmia should be looked upon as a ^^ deficiency disease" not hitherto recognized in its proper relation to diet. It is not a fat starvation, but, if it be the same condi- tion w^hich McCollum and Simmon ds have definitely shown to be readily relieved in its early stages by the administration of such foods as contain liberal amiounts of fat-soluble A, it would not be relieved by feeding with vegetable fats in any amounts. Milk, eggs, leafy vegetables and the glandular organs, are the foods which serve to protect against a short- age of this indispensable dietary component. This type of xerophthalmia is analogous to beri-beri, in that it is due to the lack of a specific substance in the diet. Beri-beri and xerophthalmia are according to McCollum and Simmonds, the only diseases refera- ble to faulty diet, which are to be explained inthis way. "' DEFICIENCY" DISEASES 93 Beri-beri is a disease common in the Orient among peoples who Umit their diet largely to polished rice and fish. It has, in recent years, been described in Laborador owing to excessive consumption of bolted flour, ^ and in Brazil among laborers whose diets were of varied character, but not judiciously chosen. ^^ It- most strikmg characteristic is a general paralysis, and it is frequently referred to, especially when pro- duced experimentally in animals, as pol^meuritis. The disease was first produced in animals by Eijkman ^^ in 1897. He discovered that when pigeons and chickens were restricted to a diet of polished rice, they steadily lost weight and in time came to manifest all the essential symptoms char- acteristic of beri-beri in man. In pigeons the disease usually appears in two or three weeks. He found that feeding rice pohshings would produce a relief of the symptoms. This result suggested that there was lacking from polished rice, something which was necessary for the maintenance of health in the bird, and that that something was present m the rice polishing?. This was the first experimental evidence that there is necessary in the diet substances other than proteins, carbohydrates, fats and inorganic salts. The observations of Eijkman attracted but little attention until Funk ^- took up the study of beri- beri in 1910. Fraser and Stanton had, as early as 1907, employed alcoholic extracts of rice polishings for the cure of experimental pol^meuritis. Funk made numerous studies directed toward the isolation 94 THE NEWER KNOWLEDGE OF NUTRITION and study of the substance which exerts the curative effect, and developed in his writings the well-knowna ''vitamine" hyj^othesis. This hypothesis postulated the existence of a similar protective substance for each of the diseases scurvy, pellagra and rickets, in addition to that which in the normal diets pro- tects against beri-beri. Funk had experimental evidence in support of his theory only in the case of beri-beri. The evidence that the other diseases which he included in the category of '^deficiency" diseases are due to the lack of specific complexes, was of the nature of clinical observations, rather than well controlled experiments. The peculiar value of butter fat was unknown to him, and he classed it among the food substances which contain no ^^vitamine" because its administra- tion to polynemitic pigeons produced no beneficial effects. ^^ Funk deserves great credit for the evidence which he secured that the amount of the substance which can be extracted from rice polishings, which is necessary to cause the relief of polyneuritis in a pigeon, is exceedingly small. A few milligrams of material which is still contaminated with impurities suffices to bring about relief in a bird which is in a helpless condition and within a few hours of death, and to make it appear like a normal pigeon. The effects seem to be out of all proportion to the amount of substance administered. Funk's studies were con- firmed and extended by the im.portant work of Williams. 1^ "DEFICIEXCY" DISEASES 95 Thei^e can be no doubt that there are two ^' de- ficiency'" diseases in the sense in which Funk and his school employed this term. One of these is beri-beri and the other the t^'pe of xerophthabiiia which ]\IcCollimi and Sunmonds have pointed out as occurring occasionally in man as the result of faulty diet, and have demonstrated to be the same condition which results in annuals as the re- sult of specific starvation for the unidentified di- etary essential fat-soluble A. It is of the greatest miportance to determine whether scur\y, pellagra and possibly rickets are likewise to be attributed to the lack of snnilar substances of a specific nature in the diet. It has already been mentioned in Chapter II that from a knowledge of the dietary properties of the oat kernel, ]McCollum and Pitz concluded from a study of experimental scur\y in the guinea pig, that this disease, while referable to faulty diet, does not result from the absence of any special sub- stance from the diet. The evidence upon which this conclusion rests has been touched upon (page 36) and will be next briefly considered. The oat kernel, when submitted to the biological method of analysis described in the first chapter, was found to contain all the chemical elements and com- plexes necessar}^ for the promotion of gi'owth and health in a mammal, but not in suitable proportions. Like other seeds it requires certain inorganic addi- tions, and its content of the unidentified fat-soluble A is enthely too small to pennit of growth, or to 9G THE NEWER KNOWLEDGE OF NUTRITION protect an animal against the eye disease, xeroph- thalmia. In addition, its proteins are not com- parable in value with those of such foods as milk, eggs and meats. The important fact was demion- strated by McCollum, Simmonds and Pitz, that if the extracts of natural foods which we have long em- ployed in our experimental work and which we desig- nate water-soluble B, contain any physiologically in- dispensable substance other than that which prevents heri-beri, the oat kernel contains all of these. This follows from the fact that they were able to induce normal growth and prolonged well-being in animals fed the oat kernel supplemented only with purified food substances, — viz: protein and inotganic salts, and a growth-promoting fat. The latter term is used to designate a fat containing the fat- soluble A. McCollum and Pitz observed that the guinea pig suffers from scurvy, not only when restricted to a diet of oats, as stated by Hoist, but likewise when fed oats and all the fresh milk it wdll consume. Jackson and Aloore ^^ made this observation independently and described it sev^eral months previous, in their excellent studies of the bacteriology^ of the digestive tract and tissues of the guinea pig, after the anim.als have developed the disease as the result of an ex- clusive oat and malk diet. Milk alone is a complete food, and suffices for the maintenance of growth and a good state of nutitrion in several species of animals, such as the rat and swine. It cannot, therefore, be "DEFICIENCY" DISEASES 97 lacking in any unidentified food substance. WTiy, then, should the guinea pig suffer scurvy when re- stricted to a diet of oats and niilk? ]McColhun and Pitz found in the guinea pigs which had died of scurv^y^ that the cecum which is a very large and very dehcate pouch thi'ough which the food must pass in going from the small to the large intestine, was always packed with putrefying feces. ^^ They decided that the mechanical difficulty which the animals have in the removal of feces of an un- favorable character from this part of the digestive tract was in some way related with the development of the disease. That this assumption was correct, was sho^^^l by the fact that the administration of hquid petrolatum, a ^'mineral" product to which no food value can possibly be attributed, served to re- lieve a certain number of animals after they were near death from the disease, while confined strictly to the diet of oats and milk which caused them to develop scurv^y. The ex|3lanation which they offered was that the Uciuid petrolatum served to improve the physical properties of the contents of the packed cecum, and thus enable the animals to rid themselves of this mass which was undergoing putrefactive de- composition. Further experiments showed that when the ani- mals were fed an oat atid railk diet, to which was added suitable doses of phenolphthalein, a ca- thartic, they could \\^thstand the diet for long periods ^\dthout developing scurvy. This, accord- 98 THE NEWER KNOWLEDGE OF NUTRITION ing to McCoJlum and Pitz, was due to the addi- tional secretion of water into the digestive tract, brought about by the cathartic, and resulted in softening the feces so that they were more easily eliminated from the cecum. It has long been known that orange juice is a very efficient protective agent against scurvy, both in man and the guinea pig. In fact it was because of the spectacular relief of the disease by the administration of orange juice or of fresh vegetables, that Funk was led to the beUef that scurvy is, like beri-beri, due to the lack of some specific chemical substance from the food supply. McCollum and Pitz further tested their theory by preparing an artificial orange juice, in which every constituent was kno^vn, and the administration of this to guinea pigs which were confined to a diet of oats and milk, on which food supply they almost invariably develop the disease. The '^ artificial orange juice "consisted only of cit- ric acid, cane sugar and inorganic salts, in about the proportions in which these occur in the edible portion of the orange. It was demonstrated that this mix- ture exerted a decidedly protective action when added to the oat and milk diet, and prevented the develop- ment of scurvy over a long period. Jackson and Moore suggested that scurvy is a bacterial disease, and they have secured experimental evidence which strongly supports that view. They found in the hemorrhagic joints a diploccocus, which may have a causal relationship to the disease. They ij SJ ^ c ^ ." 1- G o " if S.'i .S 00 o ^ 8 sj cc .55 T3 o .2 9 -, o o ;3 5c +J ^ b. T7 tJC fl :3 >. ;-i o >3 o c -kJ O r '^ 3 -rs ^ "*"■ C Si >> 'i § O 53 — a ^ g ^L^ r* -> fcr ^^ « 02 St: c3 O ^ ^ ^ fe S ^ rs o 05 CO Id 03 ''DEFICIENCY" DISEASES 99 were able to induce mild symptoms of scuny by the injection of bacterial cidtui-es into animals which were fed upon a diet which regulai-ly maintains the gmnea pig in a state of health. AlcCollum and Pitz hold the view that there may be an invasion of the tissues by organisms as the result of injuiy to the cecal wall, when the animals are debihcated. The cecum is injuied by long contact wiih. the irritating products formed by putrefactive bacteria acting on the protein substances contained in the cecum when it becomes packed \yith. feces of such a character that they cannot be ehminated. They suggested the alternative hypothesis .that there may be formed tln^ough bacterial activity, substances which are toxic, and have such pharmacological properties as cause injur}' to the walls of the capillaries of those areas in which hemorrhage is observed in scur\y. There are several problems still to be solved in con- nection with the cause of scur\y, but it seems to be satisfactorily dem.onsti'ated that it is not a ''de- ficiency" disease in the sense in which are beri-beri and the type of xerophthalmia of dietary orgin. There is, according to ^IcCollum and his co-workers, no protective substance against this disease. Diets of faulty character, and especially bacteriologically un- satisfactor>% are responsible for its etiolog>% and it is relieved by a satisfactory diet. The peculiar ana- tomical structure of the aUmentary tract of the guinea pig makes it difficult for it to thrive unless its diet contains a succulent vegetable, which gives 100 THE NEWER KNOWLEDGE OF NUTRITION the feces favorable physical characters and which makes them easy of eUmination. Hess ^^ has recently described the results of his observations on infants which were fed milk treated in various ways, and these are of great significance in throwing hght on the cause of scur\^. He points out that for a period of two years milk which had been pasteurized commercially at 165° for thirty minutes was employed in feeding the infants in his charge. For two subsequent years the dealers raised it to only 145° for thirty minutes. In his experience the former milk was more likely to induce scurvy than the latter. Hess thereafter secured raw cer- tified malk and pasteurized it at the institution for thirty minutes at 145.° Infants fed this milk did not develop scur\y in any instance, and one which showed symptoms of subacute scur\y improved on the home pasteurized milk. How did this milk differ from the commercially pasteurized milk which did show definite tendency to induce the disease? He points out that it differed mainly in the interval which elapsed between the time of the heating process and the time of consumption of the milk. In New York City, the gi'eater portion of the bottled milk sold is of Grade B, most of which is brought to the city for pasteurization, which is done soon after mid- night. ]Much of this is dehvered to the consum.er the following morning, but a part is allowed to stand until the following day before delivery. The city milk of Grade A was largely pasteurized in the coun- "DEFICIENCY" DISEASES 101 try, and since they stored the niilk for twenty-four hours after the heat treatment so as to insure a con- stant supply in case of delay in the deliveiy from the country, there was an interval of forty-eight hours between the pasteurization and the deUveiy of the milk to the consumer. Hess reproduced these con- ditions in his institution by keeping milk pasteurized at 145° for forty-eight hours on ice. Of eight in- fants w^hich were fed the milk so treated, two showed scorbutic symptoms, which were relieved by giving them orange juice. Two out of another eight which were fed milk which was kept on ice forty-eight hours after the heat treatment showed signs of scurfy. In other cases scur\y was observed in infants fed certified milk which had not been pas- teiu-ized, when the latter had been kept on the ice forty-eight hours before feeding. Ageing is, therefore, effective in causing changes in both raw and pasteur- ized milk, so that the danger of the development of scur\y in infants to wliich it is fed is increased. Boiled milk has been extensively fed to infants in various parts of the world and in the experience of some observers does not induce scur\y. The expe- rience of Hess further supports the view that boiled roilk is less liable to induce scurfy than is milk which has been pasteurized at 165° or at a lower temper- ature. jNIilk which has been pasteurized at 165° is more hable to induce scur\y than either boiled milk, or milk which has been pasteurized at lower temper- atures, as 140-145° for thirty miautes. The most 102 THE NEWER KNOWLEDGE OF NUTRITION satisfactory explanation for these results seems to be found in the bacteriological condition of the milks treated in the various ways described. Heating milk at 165° kills nearly all the lactic acid forming bacteria which normally cause the souring of milk. Heating for thirty minutes at 140° to 145° leaves some of the organisms capable of developmeat, and milk so pas- teurized will sour. In the absence of the acid formers there develop during the interval between heating and consumption the spore-forming organisms which are not killed by pasteurization. These will, in time, cause the putrefactive decomposition of the milk. Any heat treatment which kills all the acid formers leaves the milk in a suitable condition for the devel- opment of the pernicious fonns, and old milk so treated may be a menace to the health of infants, and unfit for consmiiption by adults. Boihng tends to destroy all the organisms in milk and will do so if sufficiently prolonged. Such milk may be more suitable for food than that which has been so treated as to prevent souring and yet be in a condition to permit the growth of putrefactive forms of bacteria. These results strongly support the view that there is a bacteriological factor involved in the causation of scur\y, and en.phasizes the importance of securing clean milk, and of ha\dng it so handled as to insure its deUvery in a good bacteriological condition. Milk should not be kept in the home without efficient refrigeration, and should be consum.ed before it becomes stale. Pasteurization seems, in itself, to "DEFICIENCY" DISEASES 103 have little influence in lowering the food value of milk. The staleness is the great element of danger. Pasteurization is desirable as a safeguard against such diseases as typhoid fever, tuberculosis, scarlet fever and such organisms as cause epidemics of sore throat. It does not render milk permanently harm- less. The pubUc should insist upon having its milk supply produced under hygienic conditions. Milk should then be cooled promptly so as to depress as far as possible the growth of the organisms which always find entrance through the air and from the cow and the milker. It should be carefully refriger- ated, and promptly deUvered and properly cared for in the home, and should not be allowed to age un- necessarily before use. If pasteurized, it should pref- erably receive the lowest heat treatment which will effectively destroy the pathogenic organisms, and should be dehvered as promptly as possible there- after in a suitably cooled state. Stale milk is danger- ous, especially for use in infant feeding. Pellagra. — This disease has been common in parts of Europe for centuiies. It is especially conmion in northern Italy, and has been sometimes referred to as Alpine scurv^\ It is likewise known in Spain and and the south of France. The disease was first ob- served in America in 1907, and has been steadily on the increase, especially in certain of the Southern States. In 1917 it was estimated that there were 165,000 pellagrins in the United States. Pellagra is essentially a disease of poverty, al- 104 THE NEWER KNOWLEDGE OF NUTRITION though there are many cases recoided among the well-to-do. It has been especially prevalent in the country, in villages, and in the poorer sections of cities, and is obsez'ved to occur most frequently following periods of scarcity of food. In Europe the disease was long associated with the consumption of spoiled maize as the chief article of diet, but it is now known that the eating of this grain has nothing whatever to do with its causation. All observers are agreed that the diet is of primary import in the etiology of the disease, but differences of opinion still exist as to whether there is hkewise a bacteri- ological factor involved. The trouble begins with digestive disturbances of an indefinite character, followed by soreness of the mouth, which renders eating difficult, and a per- sistent diarrhea which saps the strength of the pa- tient. Skin eruptions appear, and there are formed on parts of the body dark crusts which sometimes suppurate. In severe cases there are pronounced nervous disturbances preceding death. In its early stages pellagra yields fairly readily to dietetic treatment. Indeed it has been emphasized by clinicians that without dietary measures, there is no effective treatment, and numerous cases are re- corded in which the disease has disappeared promptly when milk, eggs and meats, string beans, together with a liberal amount of the leafy vegetables, such as cabbage, collards, and lettuce, were included in the diet.^^ ''DEFICIENCY" DISEASES 105 In the United States, especially, pellagra tends to seasonal occurrence, most new cases occurring in the spring, or better, as Goldberger has emphasized, at the end of mnter. JobUng, in his excellent survey of pellagra in Nashville, found that nearly all cases had their onset in the spring and early summer. ^^ It frequently happens that sufferers recover from their attacks of the disease during the later summer and fall, and suffer a relaspe during the following spring. Indeed the diet of many of the poorer people of the South, during the winter, consists principally of corn bread, pork and molasses. From what has been said in earlier chapters, it will be easily ap- preciated that such a combination of food-stuffs does not constitute an adequate diet, and it is significant that nearly all new cases develop after a hundred days or more of confinement to such a food supply. It should be pointed out that Jobling and Peter- son emphasize that from their observations the pellagrins, and the class from which the new cases develop, consmne relatively much carbohydrate and relatively little protein, since they make liberal use of corn bread, corn gi'its, and potatoes and biscuits made from bolted flour, together with molasses, There were some who declared that they had regu- larly eaten eggs, butter milk, milk and meat. They further point out that in the spring, summer and autumn months a great deal of green stuff in the form of turnip tops, wild mustard, green peas (seed) and green onions are eaten. The green onions are 100 THK NEWER KNOWLEDGE OF NUTRITION eaten raw, the others cooked. In addition, during the summer months much fruit, especially peaches and apples, are eaten since these are usually cheap. In commenting upon the studies of Goldberger, JobUng and Peterson point out that the poorly nour- ished individual is prone to contract many diseases and theu^ observation that there is a close relation- ship between the sanitaiy condition of the different parts of Nashville and the incidence of pellagra, tends to strongly support the view that the disease is associated with poor sewage disposal. The sani- tary conditions in those districts where pellagra is common are of the worst sort, in many instances there being little pretense made of doing anything with the excreta, which during the summer is usually covered with flies. Screening was usually absent from those houses where the disease was found. Jobling and Peterson are essentially in accord with the conclusions of the Thompson-McFadden Com- mission ^^ which made a thorough investigation of conditions in Spartanburg County, S. C, where pellagra is a scourge, and arrived at the conclusion that the disease is in some way related to a bacte- riological factor, and is probably distributed by an insect. Golderger has accom.pHshed a great work in demon- strating that the diet, when properly constituted, causes the disappearance of pellagra, and prevents its recurrence. His dietary studies have demon- strated beyond a reasonable doubt that a faulty "DEFICIENCY" DISEASES 107 diet is the most important factor in causing the de- velopmxent of the condition. He has sho\^Ti that when hberal amounts of milk and eggs and of meat, are introduced into the diet of institutions, such as insane asylums and orphanages, in which the dis- ease was previously common, they become free from it even though new cases are admitted freely and the sick are mingled with the well. He and his co- workers have likewise made heroic attempts to transmit the disease to themselves by means of the administration of the excreta and material from the lesions of pellagrins, but without success, when the experimenters were taking a satisfactory diet.-^ An expermient on man, which was carried out by Goldberger, is of special interest. A diet consisting of dishes prepared fi^om degerminated corn meal, bolted wheat flour, rice, starch, sugar, pork fat, to- gether with sweet potatoes, cabbage, collards, turnip greens and coffee, induced the appearance of what were regarded as the incipient signs of the disease by the end of five and a half months in five of eleven men, who volunteered to submit themselves to this dietar}^ regime.- Chittenden and Underhill -^ have described ex- periments in which dogs were restricted to a diet of crackers (wheat flour), cooked (dried) peas and cottonseed oil. After intervals vary-ing from two to eight months, the animals developed the t>^ical sore mouth, severe diarrhea and skin changes strikingly suggestive of pellagra in man. They were of the 108 THE NEWER KNOWLEDGE OF NUTRITION opinion that this diet caused these symptoms be- cause of the lack of some substance or substances of the class designated as 'Sdtamines" by Funk. McCollum, Simmonds and Parsons ^* demon- strated that the diet of Chittenden and Underhill, which consisted of bolted wheat flour, peas and cottonseed oil, cannot be deficient in any other uni- dentified dietary essential than the fat-soluble A, a lack of which is associated wdth the development of the eye disease, xerophthalmia. Tliis conclusion is necessary since rats were shown to fail to grow or remain in a state of health, on this mixture, and that it is rendered dietetically sufficiently com.plete by the addition of three types of purified food sub- stances, viz., mineral salts, protein, and fat-soluble A, to induce growth at the normal rate. The animals failed, however, to successfully rear young. The first limiting factor is the inorganic content. Every- thing of an unknown chemical nature which the diet must contain is present in a mixture of wheat flour, peas and cottonseed oil, but there is a relative short- age of the fat-soluble A, which is abunda>nt in cer- tain fats, and is associated with cellular structures generally in both animal and vegetable food-stuffs. McCollum, Simmonds and Parsons pointed out that although their rats failed to mxaintain satisfactory nutrition on this food mixture, unless the three kinds of supplements were added, there was no soreness of the mouth or diarrhea, such as was ob- served by Chittenden and Underhill in dogs, and are "DEFICIENCY" DISEASES 109 usually present in pellagra in man. The eyes became swollen when the diet was supplemented only by salts. An inspection of the diets described by Goldberger as common in those institutions where pellagi^a is prevalent, and the winter diets of people in those districts where there is a high incidence of the dis- ease m the spring and summer months, shows that these are composed largely of seeds and seed prod- ucts, and the amounts of leafy vegetables, milk, eggs and meat, are very small, or are enthely absent, for vaiying periods. McCollum and Sinmionds -^ have pointed out that in the exi3erimental diet with w^hich Goldberger reported having produced incipi- ent pellagi'a in man, about ninety-six per cent of the total solids of the food supply w^as derived from seed products: corn mesl, \\"heat flour, rice, starch, sugar, molasses and from pork fat, and only about four per cent from sweet potatoes and the leafy vegetables together. Such a small amount of the leaf does not suffice to make good the dietary^ deficiencies of the seed products in such a diet. These deficiencies are now well understood, and it is further known that the tubers, such as the potato and sweet potato, are not so constituted as to serve as '^protective" foods when taken together with seed products. The diets of those people who suffer from pellagra are, there- fore, deficient in three respects. They are relatively low in protein and their proteins are of relatively poor biological value, because they do not yield on 110 THE NEWER KNOWLEDGE OF NUTRITION digestion, a favorable mixture of amino-acids for the transformation into body tissues. They lack a sufficient amount of the unidentified dietary essential fat-soluble A, and also of certain mineral elements. The latter fault is in most instances limited to a shortage of calcium, sodium and chlorine. Since it is the regular practice of man to make additions of sodium chloride in the form of table salt, to his diet, the mineral deficiency in these diets may be said to be limited to the element calcium. Any one of these faults alone is sufficient to induce malnutrition when either the young or the adult animal is restricted to such diets as are common in pellagra stricken districts. Since, however, there seems to be good evidence that there sometimes occur cases of pellagra in in- dividuals whose diets have included a certain amount of such articles as AlcCollum and his co-workers have designated as PROTECTIVE FOODS, viz., milk, eggs and the leafy vegetables, the theory of an infection is supported. The prevalence of the disease in badly sewered districts supports this view. That there is a bacteriological factor involved in pellagra is further supported in some degree by the fact that McCollum, Sinmionds and Parsons ^^ ob- served only malnutrition without diarrhea or sore mouth in rats fed diets which in the experience of Chittenden and Underhill produce in dogs the gastro- intestinal symptoms seen in pellagra in man. The sloughing of the mucous membranes of the mouth, and the presence of ulcers in the intestine affords "DEFICIENCY" DISEASES 111 conclusive evidence of an infection in their dogs. McCollmn and co-workers found no unhealthy ap- pearance in the mucosa of the digestive tract, even when theii' rats were moribund as the result of being fed only wheat flour, peas and cottonseed oil. It seems probable that the difference in this respect in the two species may well be attributed to a chance infection in the one case which did not occur in the other. These observations are in harmony with the fact that not everyone who takes the poor diets de- scribed develops the disease. It seems logical in the light of all the data available, to conclude that poor nutrition predisposes to infection, and that there is an infectious agent involved in the production of pellagra. There can be no reasonable doubt that the possibility that pellagi^a is a ^^ deficiency" dis- ease, in the sense in which Funk employed this term, is definitely answered in the negative by the ex- perimental work of McCoUum and his co-workers. Rickets. — There can be no doubt that rickets is a nutritional disease, but its relation to the diet is not clear. It is characterized especially by an alteration in the growth of the bones. These become enlarged at the extremities and so soft that they bend under the stress of muscular contz^action and under the weight of the body. It is a disease of the fii'st two years of life, and is especially prevalent in children in whose diet milk is replaced too largely by cereals and other vegetable foods, not saited to the delicate digestive tract of the young child. Predisposing 112 THE NEWER KNOWLEDGE OF NUTRITION factors in many cases are undoubtedly tuberculosis and syphilis. The symptoms develop gradually. Restlessness and perspiration at night, great sen- sitiveness of the limbs, that even a light touch is extremely painful, are characteristic signs of the disease. There are gastro-intestinal disturbances, especially colic and distension of the intestine with gas, so that the abdomen protrudes. The bones become thickened, and nodules develop at the junc- tures of the ribs with the costal cartilages, forming the characteristic ^^ beaded" ribs. There is defective ossification of the skull; the teeth appear later than normal and in unusual order. Various deformities of the head, spine, chest and limbs result as the child develops. Recovery with deformity is of frequent occurrence. There must, at the present time, be an element of speculation in any discussion of the relation of diet to rickets. The well-known deficiencies from the dietary standpoint of the cereal grains and the other storage organs, together with the injury to the in- testine, which is nearly always present, as shown by the distended abdomen, and the occurrence of rickets only in early life, and so frequently in associa- tion with infectious disease, all make it unnecessary to invoke the aid of any hypothetical ^'vitamine," to a lack of which the disease may be attributed. Hess -^ has recently described the results of his dietary studies among the negro women of the Columbus Hill district in New York, whose children '^DEFICIENCY" DISEASES 113 almost all suffer from rickets. It is significant that these women are attempting, hke the very poor in many cities, to live on a diet derived from the en- dosperm of wheat, maize and rice, bolted flour, degerminated cormneal, pohshed rice, together with tubers and meats. It will be evident from the data furnished by the application of the biological method for the analysis of food-stuffs, which McCollum and his co-workers have perfected, and which was de- scribed in Chapters I to III, that there are no com- binations of those food-stuffs whose functions are those of storage organs, which will constitute a satis- factory diet for gi'owth. Muscle tissue does not tend, except in respect to the protein factor, to correct the dietary faults of such mixtures. The regular con- sumption of such diets will in the course of a few months cause a distinct lowering of the vitality of an adult and will cause even greater injury to the young child. In a later chapter it mil be showm that the milk of mothers taking such diets does not satisfactorily nourish the young. Wliat has said been above regarding the special dietaiy properties of the different food-stuffs which go to make up the diet of civilized man, and the dietaiy habits of those classes of people who suffer from the diseases which have come to be recognized as being due to faulty diet, make it easy to see that there has become fixed in the minds of students of nutrition and of the reading public, an altogether exti'avagant idea regarding the importance of the 114 THE NEWER KNOWLEDGE OF NUTRITION substances to which Funk gave the name ^'vita- muies." Of the diseases which Funk considered due to lack of unidentified substances of this nature, viz., bcri-beri, scurvy, pellagra and rickets, but one, beri-beri, has been shown to be due to this cause. In the course of the analysis by McCollum and Davis, of the problem of what chemical complexes are nec- essary to constitute the simplest diet which will serve to support growth in the young, and maintain physiological well-being in the adult, a second dietary ^'deficiency" disease in the same sense as beri-beri, was discovered, and shown to have occurred sporad- ically in man. This is the t^^e of xerophthalmia which results from a deficiency of the dietaiy essen- tial of unknowTi chemical nature, fat-soluble A. Beri-beri is due to the lack of the second unknown dietary essential w^ater-soluble B. Pellagra, scurvy and rickets do not belong in the same category with beri-beri, and there do not exist "curative" sub- stances of unknown nature for these diseases. The individual is predisposed to the development of these syndromes by faulty diet, but the faults have been shown by the biological method for the analysis of the individual food-stuffs or their mixtures, to reside in maladjustments, and unsatisfactoiy quantitative relationships among the now w^ell-recognized con- stituents of the normal diet. They are to be sought in the quality and quantity of the protein, the char- acter and amiount of the inorganic constituents, the physical properties of the residues which are left "DEFICIEXCY" DISEASES 115 after digestion, and form the feces from which the intestine must rid itself. It seems probable that the only unidentified substance which is physiolog- ically indispensable, which is not sufficiently abun- dant in the diets employed by the people of the United States and Europe where there are used in- sufficient amounts of milk, butter, cream, eggs and the leafy vegetables, is the fat-soluble A, but occa- sionally diets may be met with which contain too Kttle of the water-soluble B. Sufficient knowledge is now available to make it possible to select such foods as will mutually make good each other's deficiencies, and to combine them in such proportions as will insure the disappearance of all the diseases of man which are brought on by faulty diets. The same knowledge will, in the future, make possible an efficient utilization of feeding-stuffs for anim^al pro- duction, which will be of inestimable economic value to mankind. CH.\PTER VI THE NURSING MOTHER AS A FACTOR OF SAFETY IN THE NUTRITION OF THE SUCKLING Anyone who reflects upon the relation of the mother to her young during the suckhng period, must marv^el at the fact that during early hfe the young mammal cannot thrive on the diet of the adult. It must have milk for a shorter or longer period after birth. This the lactating animal is able to form from her food thi'ough the agency of the mammary gland. The period of dependency varies greatly in different species. Among mammals, with which the author is famiUar, the young guinea pig is born in the most highly developed state. The newborn ca\y is capable of eating grass or succulent vegetables during the first or second day of post- natal life. The young rat may be safely weaned at the age of twenty-five days, provided a highly satis- factory diet of the t^^De which sufficies for the adult is then supplied. The young pig (swdne) becomes able to eat fahly hberally of the normal adult diet at the age of six or eight weeks, w^hereas the human uifant must live largely on a milk diet during the first year of hfe and should have a liberal allowance of milk and of eggs during the entire growing period. 116 3 O -Tt O 773 THE NURSING MOTHER 117 Even eggs will not entirely replace milk during any part of this period. It is of great importance that we should understand the relationship between the character of the diet of the lactating female, and the quahty of the milk which she is able to produce. Our knowledge of this subject is still very incomplete, but experimental studies on animals have recently thrown hght on certain very importaDt phases of this problem. In order to gain information on the relation be- tween the character of the diet of the mother and the value of the milk which she produces, McCollum and Simmonds ^ carried out a series of experunents on lactating rats, whose diets were faulty in known ways, and observed the effect on the growth of the young which these mothers nursed. The mothers were fed a highly satisfactory diet until they had completed their term of jDregnancy. As soon as the young were born, the litter was in all cases reduced to four, in order that the nutritive undertaldng of the mother should in no case be burdensomxe. The mother was at once restricted to a diet which would not induce any growth whatever in a young rat after separation from the mother at weaning time. The diets of the mothers in the various experunents were faulty in respect to each of the factors which are necessary for the formation of a satisfactory^ diet, but the number of characters in which a single diet was faulty varied from oue to three. In one case the mother was fed upon a diet of 118 THE NEWER KNOWLEDGE OF NUTRITION purified protein, carbohydrate (dextrinized starch), a suitably constituted inorganic salt mixture, and an alcoholic extract of wheat germ to furnish the unidentified dietary essential, water-soluble B. This diet contained everything necessary for the nutiition of a young rat during growth, except the fat-soluble A. The problem w^as to find whether the mother could, through the agency of the mammary gland, form the missing substance, fat-soluble A. Expe- rience has shoT\Ti that the young animal after the weaning age, cannot produce it de novo, for its own preservation from any of the other constituents of its food. The results of the experiment indicated that the quantity of the fat-soluble A in the milk produced from such a diet is below the amount necessary for the promotion of the maximum rate of growth in the young. It has been shown by Osborne and Mendel,- that the body fats of beef cattle contain a small amount of the fat-soluble A. It seems certain that the body fats of an animal which has been fed for some time on a diet rich in this substance, will serve as a reserve supply of this dietary essential, which the mother can secrete into the milk. In other experiments. Chart 15, definite evidence is presented that this substance is not abundant in the milk unless it is present in the diet of the mother. The presence of some fat-soluble A in the tissues of the mother makes it especially diffi- cult to obtain milk which is entkely free from this substance. THE NURSING MOTHER 119 Through similar experiments with diets which contained the fatr-soluble A, but not the water- soluble B, evidence was secured that for a time the mother is able to secure this dietary factor from her reserve supply, but none of the growth curves in- dicated that the substance is present in the milk in adequate amount when the diet of the mother lacks it. It seems certain that neither of' these substances is present in abundance in the milk of the mother, unless it is furnished in her food. Evidence confirmatory of this view is found in the studies of Andrews ^ on infantile beri-beri. It is well known that the faulty diet of rice and fish, which fui-nishes the principal food of many of the poorer classes of the Orient, does not prevent the onset of beri-beri, and infants who nurse mothers who are suffering from the disease, likewise develop beri-beri. Andrews induced several Filipino women whose infants had just died of beri-beri, to nurse young pups, and noted that in all cases the lat- ter failed to grow, became edematous, and lost the use of their hind legs. Paralysis of the posterior extremities is one of the symptoms of the disease in man. It is evident that in the milk of these mothers there w^as a shortage of the water-soluble B, for it is a shortage of this substance which causes the development of this sjTidrome. It has been pointed out that young animals do not grow when confined to a single seed or mixture of seeds of plants, for the reason that these are all 120 THE NEWER KNOWLEDGE OF NUTRITION lacking in sufficient amounts of the inorganic el- ements, calcium, sodium and chlorine, and are too poor in the fat-soluble A to support normal nutrition. The quaUty of their proteins is likewise too poor to make them very satisfactory for the support of growth. McCollum and Simmonds have studied the extent to which the mother is able to produce milk of satisfactory character for the promotion of growth in the young, when confined to a single seed as the sole source of nutriment. Charts 15 and 16 show the effects of such diets on the growth of the young. The curves of rat 211 and of her fitter of four young (Chart 15) illustrate the remarkable growth which a mother rat is able to induce in her young when her diet is highly satisfactory, and while doing so, she is able to increase her own weight very appreciably. In marked contrast to this '' normal '^ accomplishment stands the failure of rat 738 to in- duce more than one-third the normal rate of growth in her young when restricted to rolled oats as her sole food supply. The drop in the curve of the young at the 40th day was the result of the death of the young at brief intervals. The mother lost weight regularly, showing that she was sacrificing her own tissues for the preservation of her young. Rolled oats, like the other seeds, require improve- ment in respect to three dietary factors before it becomes a complete food, and on such a faulty diet the mother produces milk which is not satisfactory for the promotion of growth in her offspring. THE NURSING MOTHER 121 Rat 843, whose diet consisted of rolled oats sup- plemented with fat-soluble A (as butter fat) induced growth in her young at a somewhat greater rate than she could have done, had she eaten oats alone, and was able to keep them alive for a longer period. The first one died on the 57th day and the others followed in rapid succession. This mother lost con- siderable weight up to the time that the 3^0 ung began to eat of the oat and butter fat diet. Young rats, after removal from the mother, cannot gi'ow at aU on this diet. Rat 899, was fed a diet of rolled oats to which was added such an inorganic salt mixture as made good the mineral deficiencies of the oat kernel. Her diet was still deficient in fat-soluble A, and to some extent in the quality of its proteins. With this food her milk was of distinctly better quality than that which can be produced on a diet of oats alone, or on oats supplemented with fat-soluble A, or on oats supple- mented vdth purified protein (rat 948) . From these results it is apparent that the first limiting factor of the oat kernel for milk production in the lactating animal is the same as in the young for growth, viz., the inorganic content of the food supply. The importance of having the inorganic content of the diet properly constituted is shown especially well in the perfonnance of the mothers 983 and 1978. The former was fed rolled oats supplemented with both fat-soluble A, in the form of butter fat, and pmified protein in the form of casein of milk. 122 THE NEWER KNOWLEDGE OF NUTRITION Even with these two additions she was able to induce less than half normal growth in her young and they began to die at the age of 45 days, and all succumbed in rapid succession. Rat 1978, on the other hand, whose diet consisted of rolled oats supplemented with a suitable salt mixture and butter fat, was able to induce growth in. her young at about two-thirds the normal rate. The improvement of the milk by the inclusion of fat-soluble A in the diet is very apparent, since the young did not die during the period of sixty days covered by the experiment, and supports the view that this substance cannot be synthesized by the mother. Rat 1019, whose diefc consisted of rolled oats supplemented with purified protein and a suitable salt mixture, shows that the mother is able to induce nearly the optimum rate of growth in her young dur- ing a period of thirty days, although her diet was very poor in the factor fat-soluble A. It should be borne in mind that the seeds, because they contain a small proportion of cellular structures in addition to their reserve food package in the endosperm, contain a small but inadequate amount of the fat-soluble A. The mother is able, when the diet of oats is corrected with respect to two factors, protein and salts, to concentrate in the milk the small content of the fat- soluble A which her diet supplies. She is probably also able to draw in some degree upon her small store of this substance which is deposited in her body fats, and supply the young with enough of it to THE NURSING MOTHER 123 enable them to reach a state of relative independence, which in a wild state would enable them to go in search of food for themselves. There is abundant experimental proof that when the protein and in- organic content of the food are of liighly satisfactory character, animals can subsist for a long period on a supply of fat-soluble A too small to prevent the onset of xerophthalmia in diets of lower biological value. These records of nursing mothers and their young make it apparent that the former is limited in a general way in the utilization of food for milk pro- duction, in the same manner as in the growing young in the utilization of food for the construction of new body tissues. She is, however, a factor of safety for her young in no small degree. It should be remem- bered that a young rat cannot grow at all when, after the weaning age, it is limited to the oat kernel, or to the oat kernel supplemented with either salts, protein or fat-soluble A alone, or on a diet of oats supplemented with both protein and fat-soluble A. In order that it may grow even very slowly it is essential that both a suitable salt mixture and fat- soluble A shall be added to the oat kernel. It can- not grow normally unless the protein factor is like- wise improved. In the records of the mothers and young shown in Chart 15, the young continued to grow in certain instances after the twenty-fifth day, the age at which they may be safely weaned when their milk supply has been of normal composition. This fact is conclusive evidence that even after the 124 THE NEWER KNOWLEDGE OF NUTRITION young become able to eat of the diet on which the mother had produced the milk on which they were able to grow — Si diet on which they would be unable to grow at all without some corrections and improve- ments — they were still receiving a supplementary milk supply from the mother. This served to correct in some measure the faulty diet of oats plus an in- complete supplementary addition. It seems certain that milk production must have been very con- siderable in amount, to thus enhance the diet of four young whose weight collectively was about half that of the miother herself. The inorganic content of all the seeds is the first hmiting factor in preventing growth in young ani- mals, and in determining the quality of the milk which can be produced from them. The young animal cannot grow at all on seeds unless one of the factors corrected includes certain salt additions, yet the mother is able to produce milk without any such additions, which is capable of inducing a limited amount of growth in the 3^oung. It is apparent that one of her most important relations to her helpless offspring is her capacity to supply it with a better inorganic food supply than she herself secures in her food, when the latter is of poor quality. The growth curves of the young of mothers whose diets consisted of the oat kernel without and with purified food additions, illustrate likewise very well the results which are observed when similar ex- periments are conducted with the wheat or maize THE NURSING MOTHER 125 kernel. They emphasize the fact that for milk pro- duction as for growth, the seeds of plants may be re- garded as closely similar in their dietary properties. It is therefore, rendered highly probable that the same analogy runs through the series of food-stuffs in their value for the production of milk of normal character. We are not to expect, therefore, that a diet consisting of even a complex mixture of seeds, tubers and roots, will produce milk of highly satis- factory character, and without undue strain on the mother. It lias been emphasized that even this Ust of foods of the class whose functions are those of stor- age organs, do not suffice even when combined with meat, to induce satisfactory growth in the young. It follows as a logical conclusion, that a lactating mother will not be able to produce milk of a very sat- isfactory character when she is restricted to such food-stuffs. It should be reiterated that there are two classes of food-stuffs which are so constituted as to correct the deficiencies of seeds, tubers, roots and meat. These are milk and the leaves of plants and they should be used very liberally in the diet. Eggs are in some degree to be regarded as comparable to these, but eggs have not the favorable mineral con- tent of the leaves and of milk, and this is one of the most important factors in which the storage organs of plants need supplementing. The question will arise in the minds of many, as to whether the inability of the young to grow on the milk produced by mothers which were Uving upon 126 THE NEWER KNOWLEDGE OF NUTRITION an inadequate diet, was not the result of the failure of the mothers to produce enough niilk rather than milk of abnormal composition. It has not been found possible to secure complete information as to the actual amount of milk which these rats secreted, but we have analogous data from domestic animals, which support the view that milk secretion remains fairly constant in the lactating animal even under very unfavorable conditions of nutrition. Babcock ^ has described experiments in which he deprived cows of common salt during lactation, other than that which they secured in their regular ration, which was of a type suitable for the dairy cow. The keen appetite of the herbivora for salt is a matter of common knowledge. Deer which are very shy will risk any danger to secure salt at their accustomed licks or from salt springs. The periods of salt deprivation varied from two to fifteen months, and some of the animals actually died, and others were saved from death by the administration of salt. In no instance was there a notable decrease in the yield of milk by these cows up to a short time be- fore they began to fail rapidly. Indeed the fat con- tent of the milk of the cows receiving an inadequate salt supply was slightly higher than in the milk of the control group. Eccles and Pahner ^ have conducted a very thor- ough experimental study of the influence of under- feeding of cows on milk production, and have studied its composition in cows whose rations were of suitable THE NURSING MOTHER 127 composition, but inadequate in amount. These results show that cows were able, during the early part of the lactation period, to maintain the milk flow undiminished for forty days, when receiving but 75 per cent enough food to meet her require- ments. Under such conditions of nutrition there was no pronounced change in the composition of the milk. During the latter part of the lactation period there was some falling off in milk production as the result of under-feeding. Ducaisne ^ in 1870, noted that during the siege of Paris, young and vigorous women were able to pro- duce enough milk to maintain their infants, and in some cases to increase their weight when they were partially fasting. These observations, as well as those of Andrews on women w^hose infants had died of beri-beri,^ all support the view that under con- ditions of faulty nutrition, it is the quality of the milk rather than the quantity which early suffers impairment. Dr. IManuel Roxas, of the College of Agriculture of the Philippine Islands, has informed the author in a private conxmunication, that the in- fants' death rate among the natives is much higher in the breast-fed than among the bottle-fed children. The occurrence of infantile beri-beri, rather than of death from starvation, further serves to demon- strate that it is milk of poor quality, rather than lack of sufficient amount of milk which is responsible for the high infant mortality in those parts of the world where the poorer classes live too largely on 128 THE NEWER KNOWLEDGE OF NUTRITION food-stuffs derived from products whose biological functions are those of storage organs, and meat. The statement which one sees reiterated so fre- quently, that breast feeding of infants is superior to the best system of artificial feeding, need3 to be qualified to some extent. There are, without ques- tion, in many parts of the world, large groups of people whose diets are of such a character that the quaUty of the milk produced by the lactating mother is not such as to make it a satisfactory food for their infants. It should be thoroughly appreciated that the human mother should have in her diet a liberal amount of milk in order to safeguard the health and well-being of her infant, and of leafy vegetables, which serve the two-fold function of a protective food and of greatly aiding intestinal elimination. That some mothers can induce a fair amount of growth in their infants while taking a faulty diet, cannot be denied, but that both mother and child suffer impairment as the result is beyond question. It is not enough that the diet shall furnish enough calories and enough protein, and shall afford variety and palatabihty. The peculiar dietary properties of the food-stuffs which enter into the diet are of paramount importance, and must be taken into con- sideration. Attention should again be directed to the observa- tions of Hess^ that the diet of the negro women of the Columbus Hill district in New York, whose diets are derived almost exclusively from seed products, THE NURSING MOTHER 129 tubers and meats, fail to nourish their infants satis- factorily as sho\\Ti by the almost universal prevalence of rickets among the latter. It is difficult for man to correct the dietary deficiencies of these products by the use of the leaves of plants as his sole protective food, because of the limited capacity of his digestive tract. ^lilk in liheral amounts should always be included m the diet of the lactating mother. CHAPTER VII PRACTICAL CONSIDERATIONS WHICH SHOULD GUIDE IN THE PLANNING OF THE DIET In the preceding chapters there were presented data, which have been obtained by biological methods, concerning the special dietary properties of the several classes of natural food-stuffs, which enter into the diets of man and animals. It is evident from the experiments described that a diet may fur- nish an abundance of protein and energy, and may be easy of digestion, and may furnish a wide variety and include several seeds or products derived from these, together with tubers, roots and meats, and may be highly acceptable to the hum.an palate and yet fail utterly to support satisfactory nutrition. In the light of such facts, it becomes apparent that a chemical analysis of a food-stuff throws no hght whatever upon certain aspects of its dietary prop- erties. It is only by biological methods that we can arrive at principles which can serve as a safe guide as to the method of procedure by means of which safe diets can be planned. In the present chapter will be discussed a number of questions which always arise in the minds of those who wish to apply the new knowledge to the planning of a suitable dietary regime. 130 THE PLANNING OF THE DIET 131 It should be understood that it is neither necessary or desirable that we should abandon the customary classification of food-stuffs on the basis of chemical composition. We must have a language of nutrition, and consider foods on the basis of their protein, carboh^'drate, fat, water and mineral content, as we have always done. We should be familiar with the quota of energ}' available from the different t^-pes of foods. We must, however, take into consideration certain facts wliich have not hitherto been considered, and concerning which a chemical analysis gives no information. One of the outstanding results of modern research in nutrition is the great difference in the biological values of the proteins from different sources. In a general way this is appreciated by aU well informed teachers of the present day, but many are still in need of clearer distinctions regarding what data m the hterature are capable of direct appUcation to practical nutrition, and what are of such a nature that they cannot be so apphed. No lack of apprecia- tion is intended of data of the latter t^^e, for they may have, and indeed frequently have a value of the first importance to the investigator in this field. As an example may be cited the laborious studies through which the amino-acids became kno\\Ti, and the data yielded by such method of analysis of the proteins as those of Fischer and of Van Slyke. Im- portant as are these results in making possible fur- ther progress, they are not of such a character that 132 THE NEWER KNOWLEDGE OF NUTRITION they can be applied, as has been frequently at- tempted, in making deductions concerning com- parative food values. It is, however, through such studies that we have arrived at a satisfactory working h^^Dothesis concerning the nature of the proteins, and have become able to appreciate why the proteins have different values in nutrition. Our analytical methods do not make possible an approximately quantitative determination of more than a third of the total number of the digestion products of the proteins. An attempt to utiUze the figures for the yield of this or that amino-acid by one or another of the proteins, as evidence of the comparative values of the proteins themselves, or of the food-stuffs from which they are deiived, will lead to entirely fallacious deduction. Such data as are tabulated in the literature for the yields of the different amino-acids, m^ake the pea and bean proteins appear superior to those of the cereal grains. AlcCollum and Simmonds have re- ported a long series of ex^Deriments with diets so planned that they were adequate in all respects, and the protein content was derived entirely from a single seed. The amount of protein in the diet was varied so as to find in one series what was the lowest per cent of protein in the food nuixture which would just m.aintain a grown rat over a period of several months without loss of body weight, and in another series, the minimum amount of protein was deter- mined which would induce in the young, half normal THE PLANNING OF THE DIET 133 and full normal rate of growth respectively. The data regarding the values of several of the more im- portant seed proteins for maintenance are of great interest. Rats can be maintained in body weight on suitably constituted diets containing 4.5 per cent of oat protein, or of millet seed protein; on 6 per cent of maize, rice or wheat proteins ; on about 8 per cent of flax-seed protein, whereas it requires about 11 to 12 per cent of the proteins of the pea or the bean to accomplish the same result. Chemical analysis shows the proteins of the pea and bean to contain all the kno\vTi ammo-acids, and none of these are present in excessive or in min- imal quantities, whereas the wheat and m^aize pro- teins yield excessive amounts of one of them in par- ticular. Glutamic acid, one of the digestion products of proteins, is present in the proteins of the muscle tissues of animals, in the case of no less than half a dozen species, to the extent of twelve to fourteen per cent. The same acid is present in the two prin- cipal proteins of the wheat kernel to the extent of nearly 40 per cent, and in the principal protein of the maize kernel to the extent of about 25 per cent. These proteins show other differences in com- position which led to the behef that they were of relatively low biological value for growth, before they were studied satisfactorily by appropriately planned feeding experiments, all of which have con- firmed this view. The observation that the split pea and na\^ bean proteins are of much less value in 134 THE NEWER KNOWLEDGE OF NUTRITION nutrition came therefore as a distinct surprise, since these results were not what were expected, in view of the tabulated yields of the several amino-acids shown by the most careful chemical analysis. The data obtained by properly planned feeding experi- ments are highly reliable, those from the chemical analysis very unsafe, from which to draw deductions. It should be understood that these values for the proteins of the seeds apply only to the proteins of the single seed when fed as the sole source of protein. When fed in mixtures of two or more proteins having individually low values for the support of growth, they may mutually make good each other's amino-acid deficiencies, and form a mixture which is better than either constituent when fed singly. Since this was to.be expected, McCollum, Simmonds and Parsons have made many feeding trials with simple com- binations of two seeds, such as two cereal grains, one cereal and one legume seed (pea, bean) ; one seed and one leaf, etc., as the sole source of protein in the diet, and have sought to find which are the m.ost fortunate combinations of the most important food-stuffs for the production of protein mixtures of high biolog- ical values for the support of growth. These trials have shown that, while such mixtures of proteins are superior to the individual foods fed separately as som"ces of protein, it has not been found possible to obtain protein mixtures from vegetable sources which even approximate the value of milk proteins, for the support of maintenance or growth. THE PLANNING OF THE DIET 135 The nitrogen-containiiig compounds of the potato have been lauded by several investigators as being of extraordinary value as a source of protein. AIc- Collum, Sinimonds and Parsons have studied the proteins of the potato, both for maintenance and growi-h, in experiments m which this tuber served as the sole source of protein, and all its dietary defi- ciencies were made good by suitable additions of purified food substances. These all indicate that when fed as the sole source of protein, the nitrogen compounds of the potato have a distinctly lower value than have the proteins of the cereal grains, oat, wheat, rice and maize. Enough has been said regarding the great dif- ferences in the values of the proteins from different sources, to make it clear that it is impossible to say how much protein the diet should contain \\dthout having a knowledge of the values of the proteins which the diet contains. Chemical methods of analysis are not yet sufficiently perfected to throw any appreciable light on the values of the mixtures of proteins which occur in our natural foods. The great attractiveness of the ^S'itamine" hy- pothesis of Funk, as an explanation for all the states of malnutrition which are referable to faulty diet, has led, m recent years, to much discussion of the question of the possible deterioration of foods during cooking, canning and dr^^ing. The demonstration by ]\IcCollum and his co-workers that there are but two unidentified dietary essentials, and but two diet- 136 THE NEWER KNOWLEDGE OF NUTRITION ary ''deficiency" diseases, due respectively to a shortage of one or the other of these substances, fat- soluble A and water-soluble B, and that there are no ''growth determinants" unnecessary for the mainte- nance of health in the adult, does not minimize the importance of this subject. The work of a number of investigators has shown that the water-soluble B, the protective substance against beri-beri, is readily destroyed when an excess of even such weak alkalies as soda are added to the food, suggests that this substance may be of an unstable character. Osborne and Mendel ^ have shown that butter fat may have a blast of steam passed through it for two hours and still retain its peculiar growth-pro- moting properties, due to the presence of the fat- soluble A. This observation is in harmony with those of McCollum and Davis, that heating butter fat at the temperature of boiling water does not affect its peculiar dietary value. It is apparent, therefore, that any conditions to which milk fats are liable to be subjected during the cooking of foods will not greatly alter its value as a source of the fat- soluble A. McCollum and Simmonds have recently (unpublished data) tested a sample of butter fat prepared from evaporated milk, furnished to them by Dr. Lucius P. Brown of New York City, and have found it very effective in relieving the xerophthalmia in rats, brought on by the lack of the fat-soluble A in their diets. It appears, therefore, that there is no great deterioration in the quality of milk fats brought THE PLANNING OF THE DIET 137 about by the processes of removal of water in the preparation of condensed or evaporated milks. They have likewise shown, as have also Osborne and Men- del, that dried milks still contain the fat-soluble A in abundance. There can be no serious objection to the use of dried or canned milks on the basis of their value with respect to this dietary essential. The situation is likewise quite clear with respect to the ordinary dried foods. Leaves such as celery tops and those of the immature alfalfa plant, when dried in the ordinaiy way, are still good sources of the fat-soluble A. The alfalfa leaves were dried in the sun and the celery tops by artificial heat in a current of air after a preliminary treatment with steam. iMcCollum and Davis - have pointed out that wheat germ can be moistened and heated in an auto- clave at fifteen pounds pressure for an hour or more without any extensive destruction of the water- soluble B, and McCollum, Simmonds and Pitz ^ have subjected soaked navy beans to similar treatment without causing any great deterioration with respect to this dietary factor. This treatment is comparable to that to which fruits and vegetables are subjected when processed in canning, and shows that the wide- spread belief that canned foods have lost these diet- ary essentials is, at least, generally without foun- dation. The cooking of beans or greens with the addition of soda, which is a common practice, may cause the destiniction of one or both of the unidentified 138 THE NEWER KNOWLEDGE OF NUTRITION dietary essentials. At least in the case of the water- soluble B, this will probably be true if sufficient soda is added to render the food alkaline. The use of soda in biscuit making will, according to Voegtlin, and Sullivan ^ cause the destruction of the water- soluble B, for they found that corn meal cooked with soda was no longer effective in causing the ^^cure'* of beri-beri in pigeons. In this connection it should be borne in mind that our ordinary foods all contain several times the amount of the water-soluble B which is necessary for the maintenance of growth and health in animals. There seems to be no valid reason why, if it is neces- sary for culinary purposes, to use soda in the cook- ing of a few foods, the practice should be discontinued. If the diet is so planned as to furnish a suitable quota of milk, and of cereals and other foods which are not so treated as to destroy the water-soluble B there is no danger of a shortage of this substance in the diet. It is now well demonstrated that with the diets employed in Europe and America there is no such thing as a "vitamine^^ problem other than that of securing an adequate amount of the substance fat-soluble A. Seeds and their products, tubers, roots and meats in the amount in which they are ordinarily consumed, do not furnish enough of this substance for the mainte- nance of an optimum state of well-being. Diets com- posed of these substances exclusively, may, when their other deficiencies are corrected, contain enough of the fat-soluble A to induce fairly good growth to THE PLANNING OF THE DIET 139 nearly the full adult size, and may long prevent the development of xerophthalmia. They do not supply enough of it to support maximum vigor over a long period, and fall short of the amount necessary under the special conditions involved in pregnancy and lactation. There is a wdde-spread belief that wheat is superior to the other cereals as a food. There is no experi- mental e\ddence that this is tiue. Rye, barley, oats and maize resemble wheat very closely in their diet- ary properties, and it is safe to say that these can entirely replace wheat in the diet of children, adults and invalids wdthout the least detriment to health. Those who have become accustomed to the use of wheat bread, are attached to it principally because of habit. Dietary habits becom.e very firmly fixed and are hard to break away from. Millions in the Orient are greatly attached to rice as a food, and feel that they cannot hve without it, whereas, we in America cannot bring ourselves to eat liberally of it in the simple and unappetizing form in which it is entirely acceptable in the Oriental. The Italian feels that no diet is satisfactory unless it contains macaroni. Garlic and other flavors which appeal to the appetite of certain peoples are disliked by others. These prejudices and many others are not expressions of physiological need, but are purely demands for something to which we have become accustomed. When properly cooked, cornmeal, oats and other cereals have never been shown to produce digestive 140 THE NEWER KNOWLEDGE OF NUTRITION disturbances. Reports that the people of Belgium, when restricted to the scanty fare which could be furnished them after the occupation of their territory by Germany, suffered from digestive disturbances from eating corn bread, are not to be taken as evi- dence that the corn products were in themselves re- sponsible for the trouble. They were the sequel of an inadequate diet which impaired the vitality. Experiments have been described, showing that bolted wheat flour is inferior to whole wheat. ^ If two pigeons are fed whole wheat and bolted flour re- spectively, while a third is allowed to fast, the first will remain in a state of apparent health for several weeks, the second will lose weight and die earlier than the fasting one. This does not mean that bolted flour is poisonous, but only that it is a more incomplete food than whole wheat. The pigeon which is fed whole wheat will succumb in the course of tim.e, for whole w^heat is not a complete food. The pigeon which fasts gradually wastes away, but slowly, be- cause all the tissues decrease in volume and its physi- ological processes slow down. The bird w^hich is fed the bolted flour dies earlier than the fasted one, be- cause the burden of digesting and metabolizing a liberal intake of food requires that his metabolic processes go on at a rapid rate. When this demand is made upon it and its diet is so incomplete that there can be no repair of its wasted tissues, it wears out the more quickly. Such demonstrations do not constitute an argument against the use of wheat flour THE PLANNING OF THE DIET 141 as a food. In so far as the latter supplies protein, energy and inorganic salts, it is a good food. AATiat we should realize is that none of our vegetable foods or the meats are complete and ideal foods. Some are more deficient than others, and their deficiencies are not all ahke. Satisfactoiy nutrition is to be attained only through the employment of the right combi- nations of foods, and in such proportions as \^dll in- sure that the resulting diet wdll be properly con- stituted. We should accept our natural foods for what they are, and make proper use of them, rather than condemn this or that one because it is lacking in some respect. It is fallacious reasoning to attempt to compare the money value of certain foods with certain others. We may safely compare the cost of the cereal grains or the legumes mth each other, or with the tubers such as the potato or the sweet potato, or with the root foods. It is not possible to compare the cost of any of these with milk or the leafy vegetables such as cabbage, cauliflower, Swiss chard, collards, Brussel sprouts, onions, lettuce, celery tops, spinach, turnip tops and other leaves employed as greens. ]\Iilk and the leafy vegetables are to be regarded as protective foods. In some degree eggs are to be con- sidered in the same class. ]\Iilk and the leafy vege- tables should be taken in liberal amounts. The leaves should not be regarded as foods of low value because their content of protein, fat and carbohy- drate is low, and the content of water high. "\ATien 142 THE NEWER KNOWLEDGE OF NUTRITION compared on the basis of chemical composition they appear inferior to seeds, but they have a pecuHar value in their high content of fat-soluble A and of mineral elements, which makes them stand in a class by themselves among the vegetable food-stuffs. No thorough studies of the dietary properties of fruits have yet been made, but from their known chemical composition and biological functions as storage organs, their proper place in the diet can be predicted. They are good sources of mineral salts and of energy-yielding foods, the sugars. They are highly palatable and exert a favorable influence on the excretory processes of the kidneys and the in- testine. Their liberal use in the diet should be en- couraged. Owing to the present shortage of certain food- stuffs, there has been a tendency to consider the in- troduction of certain new products hitherto not generally employed in a large way as human foods, and to extend their use by extolling their virtues. Conspicuous among these are the peanut press cake, which remains after the oil is extracted by pressure, the soy bean and cottonseed flour. The latter prod- uct represents a portion of the cottonseed which is prepared by first removing the oil, and afterward grinding and bolting to obtain a product free from hulls and fiber. These movements directed toward the utilization of all our food resources are laudable, but the information which is disseminated con- cerning these products by their enthusiastic pro- THE PLANNING OF THE DIET 143 moters is not in all cases accurate and sufficiently complete to serve as a safe guide to the user. They are extolled in the time- honored fashion as foods rich in protein and energy, but their exact place in the dietary is not sufficiently emphasized. There can be no doubt that the peanut is a whole- some food, and can be used to advantage in the diet of man in moderate amounts. It is likewise a good source of protein of fairly good quahty. The same can be said of the soy bean. The proteins of neither of these have extraordinary^ values. That there are no proteins of extraordinary values in the seeds of plants yet studied, is apparent from a critical and unprejudiced inspection of all of the extensive ex- permiental data available. The point to be em- phasized in this comiection, is that these are seed prod- ucts, and have in a general way the peculiar dietary properties common to seeds. Their place in the diet is therefore clear. They may be employed in moder- ate amounts along with other seeds and seed prod- ucts, provided that they are supplemented with sufficient amounts of the protective foods, milk and the leafy vegetables. With respect to cottonseed products the case is som.ewhat different. The cottonseed has long been known to contain something toxic to animals, and ex- perience has taught that cottonseed meal, a product containing the hulls, cannot be fed hberally to animals without disastrous results. Withers and Carruth*^ have conducted extensive investigations regarding 144 THE NEWER KNOWLEDGE OF NUTRITION the nature of the toxic constituent, and have iso- lated it as a substance to wliich the name gossypol has been given. It is destroyed by oxidation, and by appropriate heat treatment, and some cotton- seed products are much less poisonous than others, because of the special treatment which they have received. The author has fed cottonseed flour to a large number of animals, and is convinced that it should not be employed in the human dietary in very Uberal amounts. If the diet is appropriately con- stituted with respect to its content of the protective foods, cottonseed flour which has been thoroughly cooked, will, when used in moderation, be found to be a useful food-stuff. The data available emphasize the need for further careful studies to show how much heat treatment is necessary to render cottonseed flour harmless. Such knowledge, when available, will m.ake possible the standardization of commercial products, and will make possible the utihzation of this vast food resource. The paramount importance of maintaining and of increasing the production of milk makes it neces- sary to utilize a large amount of protein-rich foods in the dairy industry. The wisest plan is to extend the use of peanut, soy bean and cottonseed products for milk production. The cow produces much of her milk from coarse feeds, not suitable for human con- sumption, but requires liberal protein-rich supple- ments in addition. Greater emphasis should be laid upon the wisdom of a more liberal purchase of milk THE PLANNING OF THE DIET 145 by the public. This would insure the best utiliza- tion of these protein-rich products which have not as yet m many quarters found extensive use as hu- man foods. Experimental data seems to have es- tablished that the proteins of the peanut and the soy bean are of better quaUty than those of the pea or the na\^ bean. From the author's studies of the soy bean it appears that its proteins have about the same quality as those of the cereal grains, but it con- tains thi'ee times as much protein as the latter. Its content of fat-soluble A is such that a mixture of soy bean and starch wliich has the same protein con- tent as the wheat kernel, probably has about the same dietary properties as has wheat with respect to these two dietaiy factors. There is no reason why the peanut and soy bean should not be employed to a greater extent as human foods, but it should be kept in mind that good use is already being made of these products in the feeding of dairy cows, and that if the}" are T\ithdra\\^i from this application for use as human foods directly, it will not be easy to find something to take their place in the dairy mdustry. Several writers have pointed out that these seeds contain the fat-soluble A, and have exhibited growth curves which indicate that animals have taken one of these seeds properly supplemented so as to correct its deficiencies, and have been able to grow to ap- proximately the full adult size without the addition of more of this dietary essential. The reader is left with the impression that the peanut, soy bean and 146 THE NEWER KNOWLEDGE OF NUTRITION cottonseed may serve as an adequate source of fat- soluble A. This impression is an unfortunate one, for it is certain that even with diets which are com- posed largely of these seeds, the content of this sub- stance is below the optimum, and in the amounts in which they are hkely to enter into the human diet, they will never serve as a substitute for the pro- tective foods. In the enthusiastic apphcation of the biological method for the analysis of food-stuffs, by those wdth Uttle experience, after its description by McCollum and Davis in 1915,^ hasty conclusions have been drawTi in a number of instances. Mc- Collum and Simmonds have emphasized the necessity of observing over long periods, such animals as are able to grow at about the normal rate and produce a few young and rear them, when confined to ex- perimental diets. In many instances it is found that the interval between litters is too long, or the mor- tahty of the young abnormally high, the time neces- sary to bring the young to the weaning stage too long and the signs of old age appear too early, in animals which during the early part of the reproduc- tive period appeared to be nearly normal in all re- spects. They have reached the conclusion that it is necessary to observe the behavior of the second generation when confined to the diet of the parent before drawing final Conclusions concerning the quality of a diet. In many instances lack of vitaHty is first observed in the inability of the offspring to develop normally on a diet which would, in the early THE PLANNING OF THE DIET 147 life of the parent, have been considered entirely sat- isfactory. WTien observations are extended in this way, it becomes apparent that lung infections very frequently terminate the Uves of the animals, whose diets are faulty in some degree, but not so faulty as to make their effects strikingly apparent. From many questions asked by the public the au- thor has gained the con\iction that faulty deductions have been drawTi by others from experimental studies, which would lead the inexperienced reader to conclude that by the use of any seed products, or other food-stuffs of vegetable origin, whose func- tions are those of storage organs, that diets can be prepared which are so satisfactory as to make it feasible to dispense with a liberal intake of the food- stuffs which we have designated as protective foods. These can be shown to be based upon failure to fully appreciate what constitutes a satisfactory demon- stration of the adequacy of a diet. Mankind will do well to avoid such diets which may, as Golderger has suggested, place one in ^^a Hwilight' zone within which a very slight change in any of the dietary components may cause an important shift of bal- ance." McCollmn and Simmonds have reported many experiments T^ith diets so planned as to be satisfac- toiy in that all the factors but one afforded a Uberal margin of safety in offermg an abundance over the ninimal requkements of the animal,^ and the re- maining one so adjusted as to represent the actual 148 THE NEWER KNOWLEDGE OF NUTRITION niiiiimum on which the animal can subsist over a considerable period. In this way it has been possible to demonstrate that the amount of fat-soluble A may be reduced to a certain minimum without the development of xerophthalmia, whereas the same intake of this substance will not prevent the charac- teristic eye trouble when the intake of protein is likewise sufficiently lowered. They have been able to so adjust the components of the diet as to make it possible to reheve xerophthalmia either by in- creasing the content of protein or of fat-soluble A in the food, although it is the lack of the latter which is the specific cause of the disease. Such observations make it evident that it is impossible to say what is the safe minimum of any dietary factor, unless the biological values of all the other essential constituents of the diet are knowTi. This represents an actual accompHshment of planning a diet which brings the animal into the 'Hwihght" zone, w^here small shifts in the quality of the diet with respect to any factor may either distinctly stabilize the metabolic processes of the animal, or may lead to the develop- ment of a distinct pathologic state. Their studies with the types of diets just described, lead them to the conclusion that it is unwise to approach very closely the physiological minimum with respect to any dietary factor. Liberal consump- tion of all of the essential constituents of a normal diet, prompt digestion and absorption arid prompt evacuation of the undigested residue from the intestine before ex- THE PLANNING OF THE DIET 149 tensive absorption of products of bacterial decomposition of proteins can take place, are the optimum conditions for the maintenance of vigor and the characteristics of youth. Such a dietary regime can be attained only by supplementing the seed products, tubers, roots and meat, which must constitute the bulk of the diet of man, with the protective foods, milk and the leafy vegetables. The results of the study of several representatives of each of the different classes of food-stuffs has led the author to the conclusion that, while it is not de- sh^able to relegate to the background any of ihe fundamental knowledge of food-stuffs which can be obtained by chemical methods, and by resphation and digestion studies, the fundamental basis of nutri- tion can best be imparted to the public tlii'ough the adoption of a biological classification of the natural food-stuffs on the basis of their function. Foods other than milk and eggs of both animal and veg- etable origin may be arranged into groups according to whether they represent principally, functioning active protoplasm, or deposits of reserve food mate- rial, or in animal tissues, highly speciahzed contract- ile tissues. From their biological function their dietaiy properties can be fairly accurately predicted. This idea, together with the knowledge that milk, eggs and the leafy vegetables, the protective foods, are so constituted as to correct the dietary deficiencies of the seeds, tubers, roots and meat, should form the central idea in the teaching of the science of 150 THE NEWER KNOWLEDGE OF NUTRITION nutrition. It should be emphasized that the diet is a relatively complex thing, and that none of the essential constituents can be ignored in its planning, but that the observance of certain general rules of procedure will insure that any faults in the dieli will be reduced to a minimum. It is of special moment at this time to emphasize the importance of the dairy industry in its relation to the pubUc health. Mankind may be roughly classified into two groups. Both of these have de- rived the greater part of their food supply from seeds, tubers, roots and meat, but have differed in respect to the character of the remainder of their diets. One group, represented by the Chinese, Japanese and the peoples of the Tropics generally, have employed the leaves of plants as almost their sole protective food. They likewise eat eggs and these serve to correct their diet. The other group includes the peoples of Europe and North America and a few others. These have likewise made use of the leaves of plants, but in lesser degree, and have, in addition, derived a very considerable part of their food supply from milk and its products. Those peoples who have employed the leaf of the plant as their sole protective food are characterized by small stature, relatively short span of life, high infant mortality, and by contended adherence to the em.ployment of the simple mechanical inventions of their forefathers. The peoples who have made hb- eral use of milk as a food, have, in contrast, attained THE PLANNING OF THE DIET 151 greater size, greater longe\dty, and have been much more successful in the rearing of their young. They have been more aggressive than the non-milk using peoples, and have achieved much greater advance- ment in Uteratm'e, science and art. They have developed in a higher degree educational and poUt- ical systems which offer the greatest opportunity for the mdividual to develop his powers. Such development has a physiological basis, and there seems eveiy reason to beheve that it is fundamentally related to nutrition. In the United States, w^e have in the past de- rived no less than 15 to 20 per cent of our total food supply from the products of the dairy. The investigations of recent years have thrown a new light on the importance of tliis increment of our diet. It has become evident that milk is the greatest factor of safety m our nutrition, and it is certain that we could not have accomphshed what we have, had we dispensed with milk as a food. The situation of the daiiy industr>^ is at the present time precarious. The cost of feeding-stuffs and of labor have enormously increased during the last few years, and consequently the cost of milk produc- tion. Advance in the cost of milk to the consumer has been made unavoidable. Every advance in the price has, however, met with great resistance by the pubUc, and with each rise there has been a distinct drop in the amount purchased. The milk dehvered in the city of Chicago has fallen off from about a 152 THE NEWER KNOWLEDGE OF NUTRITION million and a quarter quarts daily to about seven hundred thousand quarts, within a year. Similar reductions in sales have occurred almost everywhere in the Eastern half of the country, solely because of the rise in pi ice. This has resulted in the discourage- ment of producers ever>^vhere, and in a movement toward the reduction of the number of dairy cows. There can be no doubt that there is great lack of knowledge by the people generally as to the impor- tance of milk and other dairy products in the diet. There is no substitute for milk, and its use should be distinctly increased instead of diminished, re- gardless of cost. Every possible means should be employed to reduce the cost of distribution. The necessity for the liberal use of milk and its products both in the diets of children and adults should be emphasized in order to stem the ebbing tide of its production. It has been pointed out that the value of milk as a food cannot be estimated on the basis of its content of protein and energy. Even when measured by this standard it compares most favor- ably with other foods, but it has a value as a protect- ive food, in improving the quaUty of the diet, which can be estimated only in terms of health and effi- ciency. An examination of any large groups of people in the cities, will show that where there is a high mor- tahty from tuberculosis, milk is not being used to any great extent, and in any large group where milk purchases are large this disease is not a menace. THE PLANNING OF THE DIET 153 It is well known that in institutions where tuber- culosis is successfully treated milk forms the prin- cipal article of the diet of the inmates. This has resulted from cHnical experience. There is no other effective treatment for this disease than that of providing fresh air, insisting upon rest and of height- ening the body's powers of resistance through the liberal use of milk for the correction of faults which the diet ^\ill inevitably have when it consists too largely of seed products, tubers, roots and meats. The importance of diets of this character in the etiology of tuberculosis, has not hitherto been appreciated. In the light of facts presented in the previous chapters of this book, there can be no reasonable doubt that the miportance of poor hygienic conditions and of poor ventilation have been greatly over-estimated, and that of poor diet not at all adequately appreciated as factors in pro- moting the spread of this disease. i\Iilk is just as necessaiy in the diet of the adult as in that of the growing child. Any diet which will not support normal development in the young will not support optimum well-being in the adult. ]Milk is our greatest protective food, and its use must be increased. The price must be allowed to go up, so long as the cost of production makes it necessary, and up so far as is essential to make milk production a profitable busi- ness. Unless this is done, the effects will soon be- come apparent in a lowermg of our standards of health and efficiency. INTRODUCTION TO THE LEGENDS TO THE CHARTS The data upon which the foregoing discussion of diet is based, consists of about three thousand feeding experiments. Most of these were carried out with domestic rats, but in order to demonstrate the gen- eral apphcabihty of the results of tests made on one species to other species of animals, numerous feeding tests were made on farm pigs, cattle, chickens, guinea pigs and a few on pigeons. These all indicate that the chemical requirements of these different types of animals are essentially the same. The following charts present the growth curves of rats, fed a series of diets which illustrate the type of re- sults from which the conclusions in this book are drawn. In each case the curve is the actual record of an individual which fairly represents the behavior of from four to six or mxore animals. The broken curve marked N with the sex sign (cf = male; 9 = female) represents the normal ex- pectation of growth in each sex when fed a mixed diet containing several seeds and a liberal supply of milk. Vertically the curves designate body weight ; horizontally from left to right the charts record duration of experiment, each square representing 154 LEGENDS TO THE CHARTS 155 four weeks. A break in a curve marked Y, indicates the birth of a litter of young. Although experiments are described only for the wheat, rice and oat kernel among the seeds, similar records are available for all the m.ore important seeds used as foods in America, and these warrant the statement that seeds as a class closely resemble each other in their dietary properties. A close re- semblance like^vise exists among the several leaves which have been studied, so that the edible leaves may be regarded as having in a general way the sam^e dietary properties. Chart 1. — Lot 417 shows the results of restricting young rats to a diet of purified protein, salts, carbohydrate and agar-agar, together with an extract of a natural food-stuff which furnishes the dietary factor, water-soluble B, the substance which prevents beri-beri. The diet was complete except for the absence of the fat-soluble A. As a rule there develops in animals so fed, a tj^pe of xerophthalmia, which is due to the lack of the fat-soluble A. When a fat or other natural food which is rich in cellular structures (as contrasted with reserve food materials), is added to a food mixture of this tyj)e, the resulting diet becomes capable of inducing growth. Lot 418, Period 1, shows the curves of body weight of rats fed a diet similar to that described above for Lot 417, but differing in that it contained butter fat (fat-soluble A) but lacked the extract of natural foods, and, therefore, contained no water-soluble B. On this diet xerophthalmia does not develop, but the animals ultimately lose muscular control and manifest symptoms suggestive of beri-beri in man. Growth is not possible on this diet, but everything which is needed in the diet so far as chemical analysis could show, is present. These results show the necessity of a biological analysis of food- stuffs. Gro^vth at once took place when, in Period 2, the dietary essential water-soluble B, which is likewise soluble in alcohol, was added to the diet. This dietary factor is abundant in all natural OO t^OCOTJ >> 00 (M CO lO S ^.s I (4-1 :3 o bf 73 ^§ >,bb c 2 a b£ ^ X CO c3 j*:^ -*^ • . -^ Ot^O fOO a;- O 00 ?s 1— I o ooco c O CO 00 CO (M CO 1—1 -agar rin 7 dextrin carried the hot r extract of 11 grams ol t embryo. a <^^ rl> S-i -^ O 53 rn -^-> ci X o -^ o Cl 05 O} bfiO^ c3^ o <1QH ^ ^ \ s. V ^ V \ v^ I \ ><> \ \ \ K s. \ V \ \ > \ k \ 2\ \ ^ 1 V 'uX, > I \ \ S^ 'I \ \ \ \ \ \ \ \ \ \ 1 \ \ \> \ \ 1 \ \ ]' t S W V iJ o LEGENDS TO THE CHARTS 157 foods. In investigations of the nature of those here described, it is usually added as an alcoholic extract of a natural food. Lot 419 shows the type of growth curves secured with diets con- taining both fat-soluble A and water-soluble B, in addition to the long recognized food substances, protein, carbohydrate, fat and a satisfactory supply of the inorganic elements essential for the nutri- tion of an animal. There is much reason to believe that each of the two unidentified dietary factors A and B contains but a single chem- ical complex which is physiologically indispensable, and not a group of such substances. Chart 2. — This chart illustrates the nature of the dietary defi- ciences of the cereal grains, as revealed by feeding a single variety of seed with the addition of certain purified food substances. Wheat is a typical representative of the group of seeds. The wheat kernel when fed as the sole source of nutriment, or when supplemented with protein alone or with fat-soluble A alone (in butter fat), does not induce any growth in a young animal. Wheat supplemented with the three inorganic elements, calcium, sodium a-nd chlorine, and with no other additions, induces slow growth for a time. In other words, the salt content is the first limiting factor in seeds from the dietary standpoint. These facts are not illustrated by growth curves. Lot 223 illustrates the growth of young rats when fed wheat to- gether with two purified food additions, viz., protein and a salt mixture of suitable composition. The dextrinized starch in this diet has no special significance. On this diet animals may grow to nearly the full adult size at the normal rate, and in some cases a small litter of young may be produced. The young as a rule wiU be allowed to die within a few days. On such a diet xerophthalmia will ultimately develop, and this forms the terminal event in the lives of the animals. This shows that the content of fat-soluble A in wheat is below the amount required to maintain an animal in a state of health over a long period. This fact is further illustrated by the record of rat 223-B, whose diet was Uke that of 223, except that the former con- tained 5 per cent of butter fat. Butter fat is the best known source of fat-soluble A. Lot 380, Period 1, shows how slowly growth proceeds when the diet consists of wheat, supplemented with, two purified food addi- tions, protein and fat-soluble A (as butter fat). The deficiency of »OiOO OOi-t r^ -S -ki u CO ■« c!3 m , e o "^ -»^ H o ■mW Ort^ 00000 ■^ CO (N -^ 10 CO 1— I T-l CO S u 00 d C^ CO 10 00 1-1 13 o •|! a. <=> S^ 00.2 ^ <^ -2 ^ O ^ 03 c3 c3 o CO rH '-' o .a « S 5^ cj 03 =3 ^00 c3 0^*00 00 rj^co-^l:^ CO S 1-1 ^O^Q -^ ^ f^ DUNG s A \ >■ I h > II >■ ^. \ 1 ( >^ ^ -^ V V ^ \ 4. \ \ >- \ \ 1 \ \ N \ '. \ > \ \ \ \ \ \ ^ ^1 ^ s \ \ \ '^ \ \ > ^ \ 'O - ( >\ \ s v X N V V V k \ V Nln \ n S M V u o LEGENDS TO THE CHARTS 159 the wheat kernel in certain inorganic elements is illustrated by the great acceleration of growth in Period 2, when a suitably constituted salt mixture was added to the diet of Period 1. Lot 319 shows the slow growth of a rat when fed wheat supple- mented only with the requisite inorganic salts and fat-soluble A. The proteins of the wheat kernel are not of very good quality, and must be enhanced by further protein additions before growth can be normal. Lot 223-B illustrates the fact that the optimum rate of growth is secured with wheat supplemented with three purified food addi- tions, viz., salts, fat-soluble A and protein. When wheat is improved with respect to these three dietary factors, it becomes a complete food, and supports the production of the normal number of young, and the young are successfully reared. What is true of wheat is hkewise true in a general way of the other seeds. Seeds are similar in their dietary properties. In other words, the mineral content of any seed must be improved by suitable salt additions, its protein content must be enhanced by the addition of other proteins which yield in greater abundance those amino-acids which it yields in small amounts, and in most cases additional fat-soluble A must be added in order to prevent the ultimate development of a pathological con- dition of the eyes. A liberal supply of milk will correct all the defi- ciencies of a seed diet. Chart 3. — In the process of polishing, both the germ and the bran layer of the rice kernel are rubbed off, thus removing the cellular structures and leaving only the endosperm. This consists almost entirely of proteins, starch, a small amount of fats, and of mineral elements in the form of salts. Its proteins are of relatively low value for inducing growth. Polished rice is, therefore, practically com- parable, from the dietary standpoint, to the diet of purified food- stuffs described in Chart 1. Lot 317 shows the behavior of young rats which were fed polished rice supplemented with two dietary factors, viz., a suitable salt mixture and fat-soluble A. This does not support growth, since the diet is still deficient in two respects. It lacks the second dietary essential, water-soluble B, and its proteins are of too poor quality for the support of growth in the amount supplied by 90 per cent of rice. Such a diet as that of Lot 317 will permit the development of a condition in rats similar to beri-beri in man. O "* Tt^ (M oo^ Tt^ CO (N CO c0 c3 Sh CO t-( -tj O 03 ji- rt bC ^ CO -2^. St; e 03 ooo T-H Ttl to 05 o C m CO -^j H Q^ -^ ^ -jf CO T e aj M -i!s '-H Oi o 00 i-H 03 • • ri ^ S O CO ^T3 fl coot^o OO Tti lO 00 i-i 03 ^ t<: c3 CO ■■£t3 e3 e 0^*0 03 ^ o 1^ P^Ocop:) O CO t^ o o OO Tt< O lO CO (M i-i 09 § ® c ct = ( •s. \ I ' \ V w X ( f / / \ 1 \ \ \ V \ \ \ \ 1 \ t s 4 5 1 1 \ \ \ \ J J r \ n N I \ ( \ \ \ Oi \/ \ \ \ \l \ \ I \ \ \ \ i\ o^ \ \ \ 1 \ i 1 \ \ V \ \ \ \ \ \ \ ^ \ V \ \ s \: >. \ \. ^ X ^, fH|N»S X Hf ^ ^^ O^ O O'p o 3 1-^ P^QoiCeQ 6 M V a o LEGENDS TO THE CHARTS 163 there are still other faults in the oat kernel which must be corrected before it becomes a complete food. This is illustrated by the re- maining records in this chart. Lot 625 shows that when the oat kernel is supplemented with both a suitable salt mixture and fat-soluble A, it can support growth at a good rate for three months, but does not permit the animal to reach full adult size, and leads to early failure. The protein of the oat kernel has a slightly higher value for growth than has that of either wheat or corn, but the amount furnished by 90 per cent of rolled oats is below the optimum for the support of growth in a rapidly growing species. A diet rich in rolled oats produces very hard, pasty feces, which are difficult of ehmination. This appears to be a factor of importance in preventing the normal development of the experimental animals in this series. Lot 624 further illustrates the inadequacy of rolled oats sup- plemented with both a suitable salt mixture and protein (casein). This food mixture lacks a sufficient amount of fat-soluble A, and unless there is an addition of this substance, the animals always develop the eye trouble (xerophthalmia) described on page 87. Lot 655, shows the growth curve of an animal fed rolled oats supplemented with protein, an appropriate mineral salt mixture and fat-soluble A. In this case the protein employed was casein of milk. This ration is dietetically complete, so far as its chemical composition is involved, but it did not support normal development to the full adult size. It is not possible to state just how far the stunting was due to the pasty character of the feces formed from this diet, and how far the results should be attributed to the failure of casein to supplement the amino-acid deficiencies of the oat proteins. Much better nutrition is secured with this diet when the casein is replaced by another protein, gelatin, as is shown by the records of Lot 647. Lot 647 illustrates the completeness of a diet derived from rolled oats supplemented with an appropriate salt mixture, fat-soluble A and the protein, gelatin. When Charts 2, 3 and 4 are compared, they show the striking similarity from the dietary standpoint of the three seeds, wheat, rice (unpolished) and oat kernels. It is not to be concluded from these experiments which show the faulty character of these seeds as foods, that they are undesirable constituents of the diet. Neither is it necessary or practicable to supplement in practice the seeds which we eat \sdth additions of < O COCOCO ^ jJ CO CO CO .2 COCOCO ^ 'B *i § ^ ^, o ^ 1 •• o3 <^^ 4 g>^ O e -fj (4-1 ^ CO X o <^Cii r« o oO^ Lot 1012 Ration: Period 1 Wheat Rolled oat Maize Casein Dextrin Butter fat Period 2 . and of Ca d the C O CO c T-H ^ ^ (M lO i c « CO COCO r^ " tn ^ h^ ^ ^fi^Qmc: t=OOT3 il^ «'H. CO s c c o o o c o c oo (N (M (M C^ C^ i-r-l CQ — C SI ^ ^ C n c^^p^S^K^c^ c3 t-i ce V > p 7. "*"^ o N jLX CO g 00 o CO -sS o ^ < o CO 00-2 ^ ^■^^ o o CO o o"^ o 03 o3 S W V ti O LEGENDS TO THE CHARTS 167 Lot 959 shows that the addition of fat-soluble A (as butter fat) to a mixture of three seeds, wheat, corn and oats, does not produce a food which can support growth except at a very slow rate. In Period 2, the correction of the inorganic deficiencies of the diet was followed by a prompt response with growth. Lot 1012, in Period 1, received three seeds supplemented -with both protein (casein) and fat-soluble A, but could not grow on this diet. In Period 2, the addition of the necessary salts produced an immediate response with growth. Lot 714-B, which were fed three seeds, suffered complete suspen- sion of growth. There was no response in Period 2, to the addition of fat-soluble A in butter fat. Although both protein and fat- soluble A are desirable additions to any seed diet, and are necessary before the optimum nutrition can be attained, the inorganic defi- ciencies must be corrected before any noticeable benefit can be de- rived from the correction of the other factors. (Compare 959-714-B.) Chart 6. — In marked contrast to the failure of young animals to grow on a diet restricted to seeds, one can secure very satisfactory rations from mixtures of leaf and seed. The leaf is a cell rich struc- ture; the seed, a cell poor storage organ. With this difference in function go corresponding differences in dietary properties. (See pages 43-44.) These curves illustrate the relative values for the support of growth and reproduction of diets derived from alfalfa leaf flour 40 per cent, and a seed 60 per cent. It will be seen that these corresponding leaf and seed mixtures are not of equal value. In a general way the leaves all resemble each other in their dietary properties, and form a dis- tinct group of food-stuffs as do the seeds. Lot 685 shows the possibility of securing a normal growth curve and repeated reproduction with a rat restricted to a mixture of alfalfa leaf flour 40 per cent and rolled oats 60 per cent. Of the six litters (33 young) borne by mothers which had grown up on this diet, 16 young or 50 per cent were successfully reared to weaning time. Despite the fact that an animal can grow at a rate which we may regard as normal on this food mixture, it is not of a highly satisfactory character. Rolled oats and alfalfa leaf make a better diet than the alfalfa leaf with any other seed which we have studied. It is inter- esting that these proportions between alfalfa leaf and rolled oats give better results in the nutrition of the rat than any others. ooo ooo »OC0(N CO vC \ , N Z o \ - ^ u z N'^ k < 3 ^ / \ Ui u. / X z . / f \ UI r 1- >N ^ V V I o >• N h \/ f V z U /» n f \ 111 I s < 5 \ \ lli >• \ \ -1 \ \ o 3 b. \ X u in \ \ z (fi 1 \ \ \ \ K o U 3 1/) t 2 K \ < e 7. Ul I I 1 |- 1 K \ 3 \ \ > \ u. \ V \ \ \ \ \ \ \ 1 ^\ L 0+ V z \ \ 111 \ A • z \/ UI * s. o V UI \ X q: N X k. \ ^ I5H- ^ v% n ' I »^ Is. s w V a o LEGENDS TO THE CHARTS 169 Lots 687 and 686, show that there is Httle difference in the values of mixtures of the alfalfa leaf with the wheat kernel as compared with the corn kernel. Both, in the proportions here employed, fail to induce growth at the "normal" rate, and the number of j^oung produced was approximately one-fifth that which a female rat vdW produce when her diet is of excellent quality. A well-nourished female rat may be expected to produce five htters of young. Lot 478 shows that even with a simple mixture of alfalfa leaf flour 40 per cent and polished rice 60 per cent, rats were able to grow to about 83 per cent of the normal adult size and to produce 3'oung. The rat whose curve is shown had two htters. All young from mothers which had grown up on this diet were allowed to die during the first few days after birth. Lots 688 and 717, show that combinations of peas or of cottonseed with the alfalfa leaf flour form food mixtures which can support growth at a slow rate, but are inferior to certain other combinations of leaf and seed. There are very great possibilities for improving our practices in the utiUzation of feeding-stuffs in animal production. We need exact knowledge regarding the best combinations and proportions in which to feed our natural products. Chart 7. — It is easily possible to prepare diets which are derived solely from vegetable sources, which will induce growth from weaning time to full adult size and support the production of young. Success in this direction involves the emplojTnent of suitable combinations of leaves, together with foods of plant origin whose functions are those of storage organs, \dz.: seeds, tubers, and roots. The records here presented show the most successful results which we have ob- tained with mixtures of leaf and seeds. Lot 273 shows the results of restricting young rats from weaning time to a diet derived entirely from the alfalfa leaf flour, corn and peas. The peas were cooked at 15 pounds pressure for one hour in an autoclave. The other constituents of the diet were fed raw. The female rat marked, First Generation, never grew to the full adult size, but others in the same cage with her did. The curve of this particular rat is presented because she became the great grand- mother of a litter whose ascendants for four generations ate, beyond the weaning age, nothing but this monotonous mixture of vegetable foods. ocot^o coco 03 ■^ '=> ^ t. O CO t^o o CO-< o 00 10 CO o3-^;li t-i o3 o3 •— >- ►>* I *-> o S 03 X -tJ f* bcil' :3 o3 "a A \ t h h \ A \ \ \ \ -jfN [\ -K \ \ ^v \ \ X >• V \ \ \ \ V t 12 ^ Si \ \\ \ \ '^ ) \ \ \ \ ^v^ V V \ A \ \ \ ^ 1 V \ N k \ \ z \ \ V " \ \ \l \ s \ \ \ . > K V \> \ S kN V U 9 LEGENDS TO THE CHARTS 171 This ration did not induce optimum nutrition. The number of young produced was approximately half what well-fed rats normally produce, and the mortality of the young was high. Although the breeding records were poor and the litters small, most of these young were reared. Notwithstanding this, the vigor of the fourth genera- tion appeared to be as great as that of the first. The above mixture gives better results in the nutrition of the rat than any other proportions in which these three food-stuffs can be combined. If the amount of alfalfa leaf is raised to 40 per cent or reduced to 20 per cent, and the content of corn is reduced or increased respectively, few young will be reared. The importance of knowing the exact proportions in which to combine our natural food-stuffs in order to secure the optimum results in nutrition, especially in animal production, will be evident from these results. Chart 8. — Tliis chart affords an illustration of the great differences in the degree in which a supplementary addition of protein may en- hance the value of the proteins of a natural food-stuff. The curves should be considered in pairs. Lot 493 shows the results of feeding a diet deriving its protein content entirely from the wheat kernel. The diet contained but 7 per cent of protein, an amount too small because of the relatively poor quality of the wheat proteins, to support growth at the optimum rate. The group of rats which were fed this diet grew at about half the normal rate. Lot 652 received the same diet, with 10 per cent of the carbo- hydrate replaced by the protein gelatin. The latter is one of the "incomplete" proteins, since it lacks three of the amino-acids which are essential for the nutrition of an animal. A diet which contains gelatin as its sole protein, no matter how much gelatin it may con- tain, cannot induce any growth whatever in a young animal. Lot 652, however, grew at the optimum rate. This result shows that the added gelatin made good a limited supply of certain amino-acids in the wheat proteins of the diet. This formed the limiting factor in determining the slow rate of growth in Lot 493. Gelatin is shown by this experiment to supplement well the proteins of the wheat kernel. Lots 756 and 785, show the stunting of young rats fed diets which derived their protein entirely from a mixture of peas and gelatin, and a mixture of na\'y beans and gelatin respectively. Both diets contained about 18 per cent of protein. When of good quality this ^oo o»0(MO GO O '-H 1— I t^ (M CO (M o3 B CO .Q Q? -^3 c3 O 1-^ CO O O to (M O 00 O '-t rH t^ C^ < o3 o a CO stiO CO O ID ^ Q CO C p-^'w' o o o o o o lO CO • (Nr-I CO C- U. X >- / K O II >- i \\ s d 1 \ \ \ > < \^ \ \ \ \ \ \ \ \ \ f ' \ \ \ \ >• \ y k\ V Of\ \ (0 \ \\ \ \ \ \ \ \ V^ Cm\ \ <0N (0 \ S IM V U 9 LEGENDS TO THE CHARTS 173 amount suffices for the support of normal growth. Combinations of pea proteins with gelatin, and of bean proteins with gelatin, yield amino-acid mixtures which are deficient in some way. In Period 2 in both cases, the diets differed from those of Period 1, only in that the gelatin was replaced by an equal amount of casein from milk. This change led to great improvement in the qualitj'- of the protein in the diets, and growth at once proceeded at a good rate. Gelatin does not greatlj' enhance the value of the proteins of either the pea or the bean, whereas casein does. Lots 646 and 647 show the effect on growth, of feeding a diet con- taining but 9 per cent of protein derived solely from rolled oats (Lot 646), and the same diet with 10 per cent of carbohydrate re- placed b}^ gelatin. In the former case, growth was early suspended, but in the latter, growth proceeded at the optimum rate to full maturity. This result shows that gelatin supplements the proteins of the oat kernel in a very satisfactory manner. (See discussion under Lots 493 and 652.) Lots 649 and 651, show the growth curves of rats fed, in the former case a diet which derived its protein content of about 7 per cent entirely from the corn kernel, and in the latter case the same diet ^dth 10 per cent of its carbohydrate replaced by gelatin. In marked contrast to the effects of feeding gelatin together with wheat or oat proteins, there is no improvement in the quality of corn proteins through combining these with gelatin. Gelatin does not supplement the peculiar amino-acid deficiencies of the corn kernel. Chart 9. — The records in this chart give an idea of the values of the proteins derived from mixtures of two seeds. Each of the diets described contained 9 per cent of protein. It has been estabhshed that this content of protein in a ration, when it is derived from either the wheat, corn or rice kernel alone, does not support groA^-th at a rate much faster than half the normal rate. We, therefore, fed a series of diets in which the protein content was adjusted at this level, and derived from combinations of two seeds, in order to find the most fortunate combinations of seeds as sources of proteins for gro^^'th. Normal growth is secured on diets of this character, only in those cases where the proteins of one seed enhance those of the other seed present in the diet. We have not been able to find any two seeds whose proteins, when fed together even approximate the value of the proteins of milk. O (MOROCCO HO t>- 1-H 1-H CO CQ ^^-^ c3 CO f> tn H Cm "^^ H^ SpLH;ziC)Qpq o o »^ o lO o lO o '-' T-i o c^ < lO T3 02 CO .2 -1-3 O CO O »0 (M O O 00 1-H !-< 1> CSJ lO CO 1-^ cy. " O ^ ^ >,^ 03 03 a; ^ { 1 >• \ z \ >■ Ik K n II >• .^ X I \ V v V. o\ >- s ^ J 1 1 \ 1 I 1 > > I kfc_ \ \ \ \ \ 1 \ \ \ ' \ in 'k '^>! \ ► N \ X s w V a o LEGENDS TO THE CHARTS 175 Lot 1366, derived 3 per cent of protein from millet seed and 6 per cent from the soy bean. The deficiencies of the diet, aside from the character of the proteins, were all made good by suitable additions of salts and butter fat. On this diet the growth was slow, and the animals remained undersized. On this diet three females have pro- duced four litters (23) young of which but three individuals were weaned, the others being allowed to die in infancy. This protein mixture is of relatively low biological value. Lot 1339 derived 6 per cent of protein from rolled oats and 3 per cent from flaxseed oil meal. Two females grew up on this diet. One remained sterile, and the other produced but one litter of young (7). These were finally weaned after a long period of infancy in which their growth was very slow. They were very small and runty when weaned. A protein mixture derived from these two seeds is of relatively poor quahty. Lot 1338 derived 6 per cent of protein from the wheat kernel and 3 per cent from flaxseed oil meal. Growth was below the normal rate, and two females have produced but three litters (18) young. But five of these were successfully weaned. Proteins derived from these two seeds are of relatively low biological value. They sufficed for the support of a fair rate of growth, but not for the additional strain of reproduction. This mixture must have both protein and fat-soluble A additions in order to produce the optimum results in nutrition. Chart 10. — Like the preceding chart, this shows the relative biological values of the protein mixtures derived from mixtures of two seeds. The diet was made adequate in every respect, except the protein, which was in all cases adjusted so as to form 9 per cent of the food mixture. The reason for this has been made clear in the discussion of Chart 9. Lot 1350 derived 6 per cent of protein from rye, and 3 per cent from flaxseed oil meal. Growth fell slightly below the normal expectation. One female and her daughter have produced five litters (30) young, of which but five individuals have been reared. This diet is not quite satisfactory as is shown by the reproduction records, and because of the poor quahty of its proteins, and shortage of fat- soluble A. Lot 1375 secured 6 per cent of protein from rye and 3 per cent from millet seed. One female which grew up on this diet has had a U I 02 ■ ft H^W -t-5 C o ft (4-1 o o CO -(-3 CO O O 1 = 0) CO IE S3 03 on r-H ^ -^ -^ !J5 O CO rt ^ t,_i ^ ~^ w -^ ro O CO(M O o O H! el a o cu ft o (M O 13-'^ F— '^ c3 -y ?^ S-i T^ r'-, >>' o a ft 2^ O CI i^tjlii ;3 o -^ -=J 03 >< t^ > ^,53 ft 8 O o o3 c3 S ^ ;3 o o 'S ^ ft 1 ^ C CO"^ o ^ ^•M O ,-H -^ Ht- ^ t-1^ p=3 3s hJP^ S W V U 9 LEGENDS TO THE CHARTS 177 two litters of young, all of which were allowed to die in infancy. Another female remained sterile. It is e\'ident that this combination of proteins does not form a fortunate mixture. Lot 1378 derived 6 per cent of protein from peas and 3 per cent from millet seed. Growth on this diet was slower than the normal expectation, and reproduction was below normal. Two females produced four litters (17) of young, of which but nine indi\'iduals were finally weaned at an advanced age. These were very small for their age. Combinations of pea and millet seed proteins do not appear to have a very high biological value. These histories selected from a long series of similar experiments in our records make it clear that it is not easy to find mixtures of two seeds whose proteins are of such a character as to supplement each other's deficiencies, in the 3'ields of certain amino-acids, and produce mixtures of high biological value for growth and the promo- tion of physiological well-being. In order to demonstrate the effects of a limited protein content, or of proteins of poor quality in the diet, experiments must be continued over a relatively long period of time. Observations of man or animals on such diets may lead to faulty deductions when the experiments are of short duration. Chart 11. — This chart illustrates in a general way the content of the two unidentified dietary essentials, fat-soluble A and water- soluble B, in certain natural foods. The diet in aU cases consisted principally of purified food substances, and was adequate for the support of growth, except that its content of fat-soluble A and water-soluble B was derived from the small addition of natural food. As wiU appear from the records in Chart 12, these additions of natural food-stuffs, probably furnished a sufficient amount of water-soluble B to support normal growth, so it may fairly be said that these records afford more nearly an estimation of the content of fat-soluble A in each of the natural foods emploj^ed. Lot 723 shows that 20 per cent of flaxseed does not supply enough of the fat-soluble A to support normal growth in a young rat. Lot 716, shows that 25 per cent of millet seed supplied enough of both the unidentified dietary essentials for the support of nearly normal growth, and induced sufficienth' good nutrition to make possible the production of nearly the normal number of young. The female rat usually produces five litters of young before she reaches the age of fourteen months, which age marks the end of her GO T-H O O o oi>o GC CO iO o3 ^ CO o ^3 O o o3 c3 O a •:^ t! -^3 fl to « CO CO -^ t^ ^ 5 W V U O LEGENDS TO THE CHARTS 179 period of fertility. The rat whose curve is shown, had four Utters during the first thirteen months of her hfe. The first two Utters died early, but the third and fourth, which were born after butter fat (more fat-soluble A) was added to the mother's diet, were success- fully brought to weaning age. Lot 633, whose diet derived both the unidentified dietarj^ essentials from its content of 20 per cent of alfalfa leaf, remained distinctly undersized, and produced but two Utters of young, aU of which died in early infancy. Lot 632, which received but 10 per cent of alfalfa as its sole source of fat-soluble A and water-soluble B, grew slowly, and never reached a body weight greater than half the normal adult size, and produced no young. Lot 631 was unable to grow at all when restricted to 5 per cent of aKalfa leaf as its sole source of both the unidentified dietary essentials, but responded at once with growth when the content of leaf was raised to 30 per cent. Lot 710 failed to grow weU when restricted to a diet which derived its fat-soluble A and water-soluble B from 15 per cent of hemp seed. The oil seeds, judging from the limited data available, seem to con- tain more of the fat-soluble A than do the cereal grains, but less than millet seed. The latter is richer in this substance than any other seed yet studied. Chart 12. — These records were obtained with diets which derived their content of water-soluble B entirely from the amount of natural food-stuff which each contained. The basal diet consisted of purified protein, carboh^'drate, a suitable mineral salt mixture, and butter fat to furnish the fat-soluble A. The curves give an approximate idea of the minimum amount of each of several natural food-stuffs which are necessary to furnish sufficient water-soluble B to enable a young rat to grov.^ and reproduce. Lots 645, 475 and 676 demonstrate the relative richness of the wheat kernel in water-soluble B. Even 15 per cent furnishes enough to enable a young rat to grow to approximately the full adult size, and to produce several litters of young. None can be successfully weaned on this diet. Even with 25 per cent of wheat in the diet, we have not seen a litter of young brought to the weaning age when the mother was restricted to this type of diet. When the wheat is increased to 35 per cent of the food mixture some young can be O lOO lO lO C<1 1-H i-H ooo lO c^ ^ O a) 0-3 -c -e ^ ^1 ro OT 1450 Ration: eriod 1 otato a utter fa eriod 2 aCl 1.0 ^placed eas. 2 I— 1 ^ CL, Ph Ph pq c^ z S a o > H P^ »o oo lO O 1-H i-t CO (NO o^ o \ \ V X a z 3 \ \ \ / > u. T >^"* ^ I t- lE m II > ^ A '■»c: \ c^- V 1 \ N ^•^ \ \ N o 2 \ "^ ^5 s^ - \ \ \ \ \ k V \ ^V ><« < s ^ ^ In Y r ^v \ \ 1 CM \ \ \ \ \ \ \ \ oA \i s \ \ ^J^ PhPh^UP3 S W V M o LEGENDS TO THE CHARTS 181 reared, but the mortality is still very high. With higher levels of wheat substituted for carbohydrate in this formula, the successful rearing of young becomes the rule. Lot 695 shows that 25 per cent of cooked peas in the diet as the sole source of water-soluble B furnishes a sufficient amount of this substance to enable young rats to grow well and produce young. None were reared by any of the female rats in this lot. The peas were soaked in water and heated for an hour and a quarter in an autoclave at fifteen pounds pressure, dried and ground. This treat- ment is approximately the equivalent of the heat employed in the processing of canned fruits and vegetables. There seems to be little loss of water-soluble B as the result of such heating. Lot 696 shows that 25 per cent of navj' beans, which had been soaked and heated in a manner similar to that described for peas (Lot 695), supplied enough of water-soluble B to enable rats to grow to full adult size and reproduce. Eight young out of eighteen young (2 litters) were reared by mothers confined to this diet. Chart 13. — It has been pointed out (page 46) that the tuber and the edible root are both storage organs, and, therefore, poor in cellular structures, and that their dietary properties are very closely similar to the seeds. The records of young rats which were fed mix- tures of potato and peas, supplemented in various waj's according to the biological method of food analysis, demonstrates the truth of this assertion. Lot 1405 illustrates the slow growth and early death of a rat fed a mixture of peas and potato, supplemented with the mineral el- ements, calcium, sodium and chlorine. An inspection of the remain- ing curves in the chart reveals the fact that the diet is still deficient with respect to fat-soluble A, and in no other respect. Lot 1450, Period 1, shows the failure of animals to grow when fed peas, potato and fat-soluble A. When in Period 2, pure sodium chloride (common salt) and calcium carbonate (chalk) were added, growth became possible at the normal rate. Two Utters of young have been born and all were successfully weaned. This result in- dicates that the protein content derived from peas and potato is of satisfactory character, and this conclusion is supported by the records of Lot 1414, which has been successful in growth and repro- duction when restricted to this protein mixture. To this mixture of peas and potato, both the inorganic content and the content of fat- OiOOiO lO C^ i-H t— I t^ '^• 05 S Lot 13 Ratio Potato Maize NaCl CaCOa a lO O ooo ^ t^ Oj:3 C3 -^^ O o -*J 'C.^ c'S Lot 1 Rati Period Potato Maize Butter Period NaCl were H P4 iC PI < ooo ^.2 a io»oo u -^ -^ c3^ _Q 03 OT 1415 Ration: eriod 1 otato aize ascin eriod 2 per cent o t replaced q3 3 eriod 3 aCl 1.0 an ere added h^ a,PLHSOC.eo.2 Sa.^ p: o»oo^o lO 05 1— 1 1-H CO CO ^ Iz; "* o -^^ + -(-> X -^^ /-! ^ -* c-5 o:ziO;:Qo S + + +2 CQ r/} rn m m -^^ rt ci •A >• % > r 1 h 1 \ \ i 1 \ IT u A 1 { / 1 z \ V \ \ / \ O z \ N in bJ I k \ 1 >- (A. \ \ 7. 1 > 3 U > > \ \ bl > O / 1 \ • • h \ > / • • • • ( 1 f • • • \ • • • \ \ • \ • • • • • \ / » \ \ • ) • • • • • \ \ k ( • ( • \ \ \ X V \ \ v A N \ L ^ \ K \\ ^^. ~"-^ \ \ J\ \ > N (0 2/ / \ N I s w V a o LEGENDS TO THE CHARTS 185 protein (casein) alone, or of protein, and fat-soluble A, respectively, does not make the mixture of potato and corn kernel dietetically complete. In Period 3, when the necessary salts were added, growth took place at once. The rat whose curve is shown has successfully reared two litters of young (14) and her daughter, from the first litter, has weaned a htter of seven young. The daughter has been fed exclusively upon the diet of Period 3, since she was weaned. These results make it clear that this mixture of corn, casein, potato, butter fat and the two salts, forms a very satisfactory diet. Lot 1408 shows the abihty of young rats to grow and reproduce at the normal rate and rear part of their young when confined to a diet of corn and potato supplemented with fat-soluble A and two salts, calcium carbonate and sodium chloride. This record indicates that the proteins derived from these two sources are of fairly good biolog- ical value. The diet contains but 9 per cent of total crude protein (N X 6.25). If the protein were all derived from the corn kernel, this amount would not support such a good rate of growth, and no rearing of young. From the data available in our records, it is apparent that the potato is a very valuable food, a conclusion which is in harmony with the favor in which it has come to be regarded as an article of diet for man. Chart 15. — This and the following chart describe the relation of the mother as a factor of safety in the nutrition of her young. In nearly all of these records the mother was fed during lactation, a diet which was faulty in some respect, and on wliich the young, after the weaning age, could not grow at all. The problem was to find to what extent the mother is able to take such faulty diets, and pro- duce milk of a character wliich will support growth in her young. The results show that the mother is capable under such dietary limitations of providing for her offspring a better diet for growth than she herself receives. The mothers were fed an excellent diet until they delivered their young. The htter was in all cases reduced to four, in order to make the results comparable, and in order not to place an excessive burden upon the mother. From the day the young were born the mother received the faulty experimental diet. Rat 211 illustrates the rate of growi:h of a Utter of four young when the diet of the mother is highly satisfactory. This diet con- 186 THE NEWER KNOWLEDGE OF NUTRITION tained a liberal amount of milk and of wheat, together with a salt mixture and butter fat. Rat 738 was fed nothing but rolled oats. Young after being weaned cannot grow at all on this diet. During the first 20 days the young grew slowly, then became stunted, and died between the 40th and 50th daj'^s. There are three types of deficiency in rolled oats: the inorganic content is unsatisfactory, the content of fat-soluble A is very low, and the proteins are not of very high value for growth. Notwithstanding these deficiencies, the lactating mother was able to produce milk having considerable growth-promoting properties. Rat 843 was fed rolled oats with one of its deficiencies corrected, viz : by the addition of fat-soluble A. The growth curve of her young shows that her milk was of distinctly better quahty than that which she could have produced from oats alone. The young grew faster and growth continued over a longer interval. Since the young con- tinued to grow to the 50 th day, it is evident that the mother was still supplementing the diet of oats and butter fat, which they began to eat at about the 20th day of age, with a considerable amount of milk which corrected the inorganic content of the oat kernel, for without the addition of calcium, sodium and cholrine, rolled oats cannot support growth, even when its other deficiencies are corrected. Rat 983 did no better with her young on a diet of oats to which both protein and fat-soluble A were added, than did rat 843, with- out the protein addition. The first limiting factor for the mother in milk production is the inorganic content, just as it is for growth in the young. Rat 899 did remarkably well in inducing growth in her young when her diet consisted of rolled oats and a suitable addition of salts for the correction of the inorganic deficiencies of the oat kernel. The seed is not entirely free from fat-soluble A, and the mother seems to have a reserve supply of this substance in her tissues which she can, for a time, contribute to her milk. Rat 1978, which was fed oats supplemented with salts and fat- soluble A, induced growth at a fairly good rate in her young. The 60 per cent of oats in her diet furnished but 9 per cent of protein, and this did not suffice, because of its relatively low value, for the production of a normal milk supply. The growth of these young after the time they became able to eat of the mother's food supply, was much more rapid than it would have been had they not been LEGENDS TO THE CHARTS 187 getting a supplementary milk supply from the mother during the period covered by the growth curve. Chart 16 contains further records of the growth of young which were suckling mothers on diets derived from rolled oats, supple- mented in various ways. Chart 16. — Continuing the records described in Chart 15. Rat 948 shows the failure of the young to develop beyond a lim- ited degree on a diet of rolled oats supplemented with protein only. The behavior of these 3'oung is comparable to that of Lot 738, Chart 16. The two most serious deficiencies of the oat kernel for milk production as for growth in the young, are the inorganic factor and the shortage of fat-soluble A. It was shown in Chart 8 that oat proteins combined with gelatin, form a highly satisfactory protein mixture. This is confirmed by the growth at half normal rate of the young of rat 949, whose diet consisted of rolled oats and gelatin. Young rats cannot grow at all on this mixture. The mother is able to take such a faulty diet, and furnish milk of such a character as will safeguard her young in a most remarkable degree. Her limitations are, however, easily apparent. Rat 984 did slightly better in extending the lives of her young when she was fed rolled oats plus gelatin plus butter fat (fat-soluble A), than did rat 949, on the same food, minus the butter fat. It should be remembered that young rats cannot grow at all, if when, after being weaned, they are confined to this diet. The role of the mother as a factor of safety in the nutrition of her young is easily seen. Rat 1020, which was fed oats, gelatin and salts, was limited only with respect to the relative shortage of fat-soluble A in her diet. Nevertheless, she was able to produce milk which could induce growth at a fairly good rate in her young. Rat 1019, was fed a diet which differed from that of 1020 only in containing casein. This appears to have had a slightly beneficial effect. Rat 980 was fed rolled oats plus 20 per cent of skim milk powder. This amount was not sufficient to correct the inorganic deficiencies of the diet, and failed to supply enough fat-soluble A to render the diet satisfactory for milk production. It seems probable that the sodium chloride content and fat-soluble A in the skim milk powder o O i6 -c + + + •7:2 00 o o o 00 O d ^ r^ 1 'S "S ^ 'c^'S + K ^ ^ ^ 73 c3 o c o rt oOOOOO CO 73 50 73 K 03 -t^ -t-s -t^ -tJ -t^ -tJ c3 c3 rt -r: je rt ^OOOCCO ^ -C -rr -^ -d ^ -:i ^ c c~"5'c3 •7 (^ ryJ ^^ ^-- <%-- ~s ill > r' 1- J Z ^ \ I / \ Sv in \ 2 u. ( ' f > V \ > IT D U ■••5 > K u • J J f Vs > \ \ ^ \ V / \j 1/ 1 / \ \ / r ; 1 ° '•.. \ • • •••.. ••••.., \" > r • 'n % •• a • • • • • ^N ^. • o • — • ( • • o V \ ^, ( \ N 1 a / (i ^» -^ N y '1 t ^ »•» ^ ^ \ , \ \ \ ) N. ^ V \ c \ \ N - o o a \ 1 i-iO O O '^ i-H (M GO OOC: O 00 CiCi s w V a o LEGENDS TO THE CHARTS 189 were the limiting factors in preventing the production of normal milk in this case. In answer to the question as to whether the failure of the young to grow on the milk they received in these experiments, was not the result of insufficiency in quantity rather than quaUty of milk, we have the observations on cows, which were fed insufficient food during lactation, and in other experiments, in which cows were starved for common salt for periods of eight to fifteen months, and actually died or came near death from salt starvation. Under such conditions the milk flow was kept up over a long period in a most surprising manner. We have further evidence that the young rats in the experiments described, continued in some instances to grow long after they be- came able to eat of their m.other's food, when the latter was of such a character as to permit of no growth whatever, had it not been supplemented with a considerable amount of milk from the mother. When it is considered that in some of these cases the young weighed more than half as much as the mother, it must be admitted that the milk production, even in these greatly prolonged periods of lactation, while the mothers were taking faulty diets, must have been very considerable. The relation between the character of the diet of the nursing mother and the character of the milk she produces has been dis- cussed in Chapter 6. BIBLIOGRAPHY Chapter I 1. Fischer: Chemistry of the Proteins, Mann. 2. Osbome, T. B.: The Vegetable Proteins, Monographs on Biochemistry, Longmans, Green and Company. 3. Atwater, W. A.: Bulletin 28, United States Department of Agricultm-e. 4. Eijkman, C: Arch. f. Hyg., 1906, hdii, 150. Arch. path. Anat., 1897, cxlviii, 523. 5. Henriques and Hansen: Zeitschr. fiir physiol. chem., 1905, xliii, 417. 6. WiUcock, E.G., and Hopkins, F. G.: Jour. Physiol., 1906, XXXV, 88. 7. Wise. Agric. Expt. Sta., Research Bull., No. 17 (1911). 8. McCoUum, E. V., and Davis, M.: Jour. Biol. Chem., 1913, XV, 167. 9. Stepp, W.: Biochem. Ztschr., 1909, xxii, 452; Ztschr. f. Biol., 1912, Ivii, 135; Ibid, 1912-1913, lix, 366. 10. Hopkins, F. G.: Jour. Physiol., 1912, xliv, 425. 11. Funk, C: Lancet, London, 1911, ii, 1266. 12. Eraser, H., and Stanton, A. T.: Lancet, London, March 12, 1910, 733; The Etiology of Beri-Beri, Study 12, from the Institute for Medical Research, Federated Malay States, 1911. 13. McCollum and Davis: Jour. Biol. Chem., 1915, xxiii, 247; McCollum, E. v., Simmonds, N., and Pitz, W.: Ibid, 1916, xx^/, 105. 14. Funk and Macallum: Jour. Biol. Chem., 1915, xxiii, 419. 15. Henry, W. A.: Wisconsin Agric. Expt. Sta., Annual Re- port, 1889, 15. 191 192 BIBLIOGRAPHY 16. Funk, C: J. State Med., 1912, xx, 341; Biochem. Bull., 1915, iv, 304. 17. McCollum and Davis: Jour. Biol. Chem., 1915, xxiii, 181. 18. McCollum and Davis: Jour. Biol. Chem., 1915, xxiii, 231. 19. McCollum, E. V., and Kennedy, C: Jour. Biol. Chem., 1916, xxiv, 491. 20. Osborne, T. B., and Mendel, L. B.: Jour. Biol. Chem., 1913, xvi, 431. Chapter II 1. McCollum, Simmonds and Pitz: Jour. Biol. Chem., 1917, xxix, 341. 2. Smith, Theobold: Bureau of Animal Industry, Bacilli in Smne Disease, 1895-1896, 172. 3. Hoist, A., and Frohch, T.: Z. Hyg. u. Infektionskrankh, 1913, Ixxv, 334. 4. McCoUum and Pitz: Jour. Biol. Chem., 1917, xxxi, 229. 5. McCollum and Simmonds: Jour. Biol. Chem., 1917, xxxii, 181. 6. McCollum and Simmonds: Jour. Biol. Chem., 1918, xxxiii, 55. 7. Hart, E. B., McCollum, E. V., Steenbock, H., and Hum- phery, G. C: Wise. Agric. Expt. Sta. Research Bull., 17, 1911. Hart and McCollum: Jour. Biol. Chem., 1914, xix, 373. McCollum and Davis: Jour. Biol. Chem., 1915, xxi, 615. McCollum, Simmonds and Pitz: Ibid, 1916-1917, xxviii, 211. 8. Hart and McCollum: Jour. Biol. Chem., 1914, xix, 373. McCollum, Simmonds and Pitz: Ibid, 1916, xxviii, 153. 9. McCollum, E. V., Simmonds, N., and Parsons, H. T.: Unpublished data. 10. McCollum, E. V. : Jour. Am. Med. Assn., 1917, kviii, 1379. Harvey Lecture Series 1916-1917 — also — Unpubhshed data. BIBLIOGRAPHY 193 U. iMcCoUum, Simmonds and Pitz: Jour. Biol. Chem., 1917, Xxix, 521. -r^. , /-,! ini7 12. McCoUum, Simmonds and Pitz: Jour. Biol. Chem., 1917, XXX, 13. Chapter III 1. Slonaker, J. R.: Leland Stanford Junior University, Pub. rniv. Series, 1912. ^. , r^^ ini7 2. McColliun, Simmonds and Pitz: Jour. Biol. Chem., 1917, XXX, io. . 1 ni « 3. TylcCollum, Simmonds and Pitz: Am. Jour. Physiol., 191b, xliv, 333. .. 4 E^^'ard J. M.: Proc. Iowa Acad. Sci., 191o, xxu, cJ/o. 5'. Loeb, J.: The DjTiamics of Living Matter, New York, 6. Howell, W. H.: Am. Jour. Physiol., 1899, ii, 47; 1902, vi, 181. Chapter IV 1. McCollum, E. v.: Jour. Biol. Chem., 1914, xix, 323. 2. jNIcCoUum and Simmonds: Jour. Biol. Chem., 1917, xxxii, 347. „ 3 McCollum and Davis: Jour. Biol. Chem., 191o, xx, 4io. 4. McCoUum, Simmonds and Parsons: Unpublished data. Chapter V 1. McCollum and Kennedy: Jour. Biol. Chem., 1916, xxiv, 491. 2. Osborne and Mendel: Jour. Biol. Chem., 1913, x^i, 431._ 3. McCollum and Simmonds: Jour. Biol. Chem., 1917, xxxu, 347. 4. ISIcCollum, Simmonds and Parsons: Unpublished data. 5. Herdhka, A.: Bulletin 34, Bureau of American Etlmology. 194 BIBLIOGRAPHY 6. Mori, M.: Jahrb. Kinderheilk, 1904, lix, 175. 7. Bloch, C. E.: Ugeskruft fiir Laeger, 1917, Ixxix, 349, cited from Jour. Am. Med. Assn., 1917, lx\iii, 1516. 8. Czerny, A. and Keller, A.: Des Kindes, Leipsic, 1906, pt. 2,67. 9. Little, A. D.: Jour. Am. Med. Assn., 1912, Iviii, 2029. 10. Walcott, A. M.: Jour. Am. Med. Assn., 1915, Ixv, 2145. 11. Eijkman, C: Arch. f. Hyg., 1906, Iviii, 150. Arch. Path. Anat., 1897, cxlviii, 523. 12. Funk, C: Lancet, London, 1911, ii, 1266. 13. Funk and Macallum: Jour. Biol. Chem., 1915, xxiii, 419. 14. Williams, R. R.: Jour. Biol. Chem., 1916, xxv, 437; 1916, xxvi, 431; 1917, xxix, 495. 15. Jackson, L., and Moore, J. J.: Jour. Infect. Dis., 1916, xix, 478. 16. McCollum and Pitz: Jour. Biol. Chem., 1917, xxxi, 229. 17. Hess, A. F.: Am. Jour. Dis. of Children, 1917, xiv, 337. 18. Goldberger, Joseph: Jour. Am. Med. Assn., 1916, Ixvi, 471. 19. Jobling, J. W., and Peterson, W.: Jour. Infect. Dis., 1916, xviii, 501. 20. Thompson-MacFadden Commission, Siler, J. F., Garri- son, P. E.,and McNeal, W. J.: Archiv. Int. Med. Oct. 1914, p. 453; Journ. Amer. Med. Assn. Sept. 26, 1914, p. 1090. 21. Goldberger, Joseph: Public Health Reports, November 17, 1916, pp. 3159-3173. 22. Goldberger, Joseph: Public Health Reports, Nov. 12, 1915, p. 3. 23. Chittenden, R. H., and Underbill, F. P. : Am. Jour. Physiol., 1917, xliv, 13. 24. McCollum, Simmonds and Parsons: Jour. Biol. Chem., 1918, xxxiii, 411. 25. McCollmn and Simmonds: Jour. Biol. Chem., 1917, xxxii, 29. 26. Hess, A. F. : Jour. Am. Med. Assn., 1918, kx, 900. BIBLIOGRAPHY 195 Chapter VI 1. McCollum and Simmonds: Am. Jour. Phys., 1918, xlvi, 275. McColluni, Simmonds and Pitz: Joiir. Biol. Chem., 1916, xx\ii, 33. 2. Osborne and Mendel: Jour. Biol. Chem., 1915, xx, 379. 3. Andrews, V. L.: Philippine Jom*. Science, Series B, 1912, vii, 67. 4. Babcock, S. M.: Twenty-Second Annual Report of Wis- consin Experiment Station, 1905, 129. 5. Eckles, C. H.,and Palmer, L. S.: Missouri Agric. Expt. Station Research Bull., 25, 1916. 6. Ducaisne, E.: Gaz. Med., Paris, 1871, 317. Chapter VII 1. Osborne and Mendel: Jour. Biol. Chem., 1915, xx, 381. 2. McCollum and Da^^s: Jour. Biol. Chem., 1915, xxiii, 247. 3. McCollum, Simmonds and Pitz: Jour. Biol. Chem., 1917, xxix, 521. 4. Sullivan, M. X., and Voegtlin, C. : Jour. Biol. Chem., 1916, xxiv, xvi. 5. Simpson and Edie: 1911-12, Ann. Trop. Med. and Parasit., V, 321. Ohler: Jour. IVIed. Research, 1914, xxxi, 239. 6. Withers and Carruth : Jour. Agric. Research, 1915, v, 261. Jour. Biol. Chem., 1917, xxxii, 245. 7. McCollum and Da\as: Jour. Biol. Chem., 1915, xxiii, 231. 8. McCollum and Simmonds: 1917, xxxii, 181. INDEX Alfalfa flour, 41, 167, 169, 179 Alkaloids, 4 Amino-acids, 5, 74, 75 Appetite, importance of in the selection of food, 64 Barley, 38 Bean, navy, 38, 181 Bean, soy, 38, 175 Beri-beri, 7, 20, 28, 83, 90 Biological method for the anal- ysis of food-stuffs, 20, 21, 56, 113, 161 Butter fat, 16, 89 Carnivora, dietary habits of, 78 Cereal grains, 157, 161 Chittenden and Underhill, stud- ies of pellagra, 107 Corn, 10, 173 Cotton seed flour, 142, 143 Deficiency diseases, 83-87, 91 95, 114 Diet and disease, 6, 7 Diet, essential factors in, 31 Diet of nursing mother in rela- tion to the quality of her milk, 116-129, 185-189 Diet, planning of adequate, 130 Diet, monotonous, 7 Dietary essentials, nomencla- ture of unidentified, 32 Dietary essentials, chemically unidentified, 23, 34, 47 Dietary habits, 139 Diets from single plant sources, 10 Diets, simplified, 9, 14, 15, 16, 19, 155 Disease and diet, 6, 30, 36, 87, 95, 103, 139 Diseases, deficiency, 83-87, 91, 95, 114 Eggs, 80 Eijkman, 7 Eward, studies on appetite, 64 Fats, 2, 3, 4 Fats, butter, 16 Fats, egg yolk, 16 Fats, lard, 16 Fats, vegetable, 16 Fat-soluble A, 23, 34, 47, 89, 145, 155 Flax seed, 38 Food analysis, 5 Foods, effect of cooking on, 135-138 Foods, physical properties of, 15 Foods, protective, 82, 141, 147, 149 Foods-stuffs, biological analysis of, 20, 21, 56 197 198 INDEX Food-stiifTs, supplementary re- lationships among, 61, 71, 81 Fraser and Stanton, 19 Fruits, 7, 142 Funk, 19 Gelatin, 171 Glandular organs, 79 Gliadin, 8 Goldberger, studies of pellagra, 105-107 Growth, impetus to, 72 Henriques and Hansen, stud- ies of simplified diets, 8 Hess, studies of scurvy, 100 Hoist, studies of scurvy, 34 Hopkins, studies of simplified diets, 18 Hormones, 85 Inorganic salts, importance of, 4,22 Iron, 69 Jobling and Peterson, studies of pellagra, 105-106 Kafir corn, 38 Leaf, dietary properties of, the, 41, 44, 53, 77 Leaf and seed mixtures, dietary properties of, 61, 167 Lipoids, 3, 17 Meats, 6, 8, 76 Milk, 6, 8, 76 Milk, place of in the diet, 150- 153 Milk, production, 12 Milk, quality of, as influenced by diet, 116-129, 185-189 Millet seed, 38, 175, 177 Muscle tissue, 6, 8, 76 Nomenclature of the chemically unidentified dietary essentials, 84 Osborne and Mendel, 87 Pasteurization of milk, 100-103 Peanut, 142 Peas, 38, 177, 181 Pellagra, 7, 30, 103 Pellagra-producing diets, 108 Polyneuritis, 19, 20, 28 Potato, proteins of, 135, 181 Proteins, 2, 3, 4, 5 Proteins, biological values of, 5, 24, 74, 75 Proteins, quality not shown by chemical analysis, 113 Rat, domestic, 14 Rat, domestic, growth of, 14 Rat, reproduction in, 14 Rice, dietary properties of, 27, 38, 159, 161 Rickets, 111 Roots, edible, 47 Rye, dietary properties of, 38, 175 Salts, 4 Scurvy, 7, 30, 34, 36, 37, 95-103 Seed, biological properties of, 53 Seed, and leaf mixtures, dietary properties of, 61 INDEX 199 Seeds, dietary properties of, 6, Variety not a safeguard in nutri- 165 tion, 66 Slonaker, studies of vegetarian Vegetable oils, 16 diet, 57 Vegetables, 6, 7 Smith, Theobald, scurvy in the Vegetarian diet, 50, 53 guinea pig, 34 Sodium, lack of sufficient, in Water, 4 seeds, 23, 49 Water-soluble B, 29, 34, 47, Starch, 2, 3, 4 155 Stepp, studies of dietary prop- Wheat and other cereals com- erties of lipoids, 17 pared, 139 Wheat, dietary properties of, Thompson-McFadden CommJs- 10, 20, 21, 38, 157, 159, 171, sion, studies of pellagra, 106 175, 179 Tubers, dietary properties of. Wheat flour, bolted, 140 6, 45 Wheat flour, whole, 140 Unidentified factors in the diet, Xerophthalmia of dietary origin, 17, 18 87, 139 Printed in the United States of America T HE following pages contain advertisements of books by the same author or on kindred subjects Organic Chemistry for Medical Students By ELMER V. McCOLLUM, Ph.D. Professor of Bio-Chemistry, Johns Hopkins Medical School Illustrated. Cloth ^ i2mo. %2.2£ The author has based this work on the new bio- logical methods of teaching chemistry to medical students. The work is developed from Dr. InIcCoI- lum's unusual researches and experiments and the subject matter is presented with great clearness and attention to teaching principles. It is unique in scope and methods and is designed for the use of both medical and pre-medical students. THE MACMILLAN COMPANY Publishers 64-66 Fifth Avenue New York Chemistry of Food and Nutrition New and Revised Edition By henry C. 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ROSE Everyday Foods in War Time ^-^^ This little book was written in response to a re- quest for "a war message about food." It gives a simple explanation of the part which some of our common foods play in our diet, and points out how the necessary-^ saving of fat, fuel, sugar, and meat can be made without a loss of health or strength. There are chapters on the Milk Pitcher in the Home; Cereals We Ought to Eat; Meats We Ought to Save; The Potato and Its Substitutes; Are Fruits and Vegetables Luxuries? Sugar and Spice and Everything Nice; On Being Economical and Pa- triotic at the Same Time. Feeding the Family ^^^^ This is a clear concise account in simple everyday terms of the ways in which modern knowledge of the science of nutrition may be applied in ordinary life. The food needs of the members of the typical family group — ^men, women, infants, children of various ages — are discussed in separate chapters, and many illustrations in the form of food plans and dietaries are included. The problems of the housewife in tr>dng to reconcile the needs of different ages and tastes at the same table are also taken up, as are the cost of food and the construction of menus. A final chapter deals with feeding the sick. THE MACA/[ILLAN COJMPANY Publishers 64-66 Fifth Avenue New York War Bread By ALONZO E. TAYLOR Professor of Physiological Chemistry, University of Penn- sylvania; member of the United States Food Admin- istration ^ ^^ S.60 Dr. Taylor states that it is his purpose to make clear just what must be accomplished in order that we may give to every member of the allied people his full share in our pooled food stuff at the lowest comparable cost and with the least labor. With this in view, he takes up the following topics: What the Allies Need; What We Possess; Why We are Limited in Wheat; Food Value of the Different Grains; Ways of Stretching Wheat; and Waste of Wheat. The Food Problem By VERNON KELLOGG and ALONZO E. 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