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 THE GHEMISTRY OF FOOI). 
 
 
 ■i ^x 
 
 TWO LECTraKS DEI.lYEllEI) HEFOHE THE 
 
 OTTAWA FIELD NATURALISTS' (^LUB, 
 
 DY 
 
 FRANK T. SHUTT, M.A., K C S., F. J. C. 
 
 ^ 
 
 K'^. 
 
 
 ^'^*^<JL.3:ai'aV^tf*"'*'-'^Jto-'^irr*''^'' '^^*^-:': 
 
 
I Reprinted from Tkk Ottawa NAitufi.tsr, Dec. 1891. 
 
 MONDAY AFTERNOON LECrURES. Nos. 7 & 8. 
 
 I 
 
 The Chemistry of Food. 
 
 Bv Fkank T. Shu rr, M.A., F.C.S., F.I.C4 
 
 (Two lectures delivered Feb. 2jrd, and March 2nd, l8gi.) 
 
 He, indeed, would be an unreflecting and unthanklul individual 
 who would not be willing to admit that the higher civilisation of later 
 times has given us great and innumerable blessings. \Vc mi^ht, per- 
 chance, find such an one amdng ihosw' who have grown up amid the 
 comforts and luxuries of wealthy modern life, an unconscious re- 
 cipient of good things and ignorant of the life of our forefathers ; or 
 among those who, from long-continued poverty or degradation, can 
 hardly he said to enjoy those bless'ngs. To recount the triumphs of 
 science and enterprise^— not to speak of other and not less important 
 factors of our civilization — during the last fifty years would be a 
 more than Herculean task.' Triumphs of the Natural and'' Applied 
 Sciences — 'great ttiumphs irf the art of healing and no less great in 
 electricity, and mechanics, and agriculture, and a host of sister sciences 
 — triumphs that have added to our comforts and have alleviated our 
 sufferings, attend and surround us on every side. 
 
 But yet, while confessing all this with ready lips, a moment's serious 
 reflection tells us that there is scarcely Ji blessing without its concomi- 
 tant evil— an evil too often the result of the abuse of the blessing. 
 Evils whose origins may easily be traced to the wrong or excessive use 
 of things in themselves good and wholesome, pervade all ranks of 
 society. It is only when we view exclusively this side of the picture — 
 as too many of us occasionally do — that we are apt to conclude tha^ 
 our boasting of the achievements of the nineteenth century and the 
 so-called betterment of the "-ace, is worse than vain. 
 
 But what has all this to do with the subject under discussion — the 
 chemistry of food ? A little careful thought may show us the applica- 
 bility of these remarks as an introduction to a lecture on such an 
 important matter as food; for although my title might be considered, 
 strictly speaking, to confine me to the composition of foods, I propose 
 to incorporate with the chemistry somewhat of the physiology of food. 
 
3 
 
 'A . 
 
 
 U ' 
 
 t 
 
 In I his way I hope to make these lectures not only more interesting but 
 more instructive than ihry othe'^wise might be to a general audience. 
 Hy learning the functions of the constituents of foods in the system we 
 may— as we shall see more clearly later on— be t!ie better able to prac- 
 tise economy and preserve health. 
 
 To many of us civilized life has brought with it the accumulation 
 of wealth, and wealth grants us comparative leisure and the means of 
 obtaining not only necessities but luxuries in abundance. It gives us 
 plenty of good, nutritious and palatable food, but it also gives us the 
 opportunity of indulging in those luxuries of the table, the excessive use 
 of which is so disvistrous to our health. Leisure takes from us the 
 necessity of that wholesome amount of exercise, which promotes a nor- 
 mal and healthful condition of the system. 
 
 On the other hand the cond.tions of society make us ambitious and 
 encourage us to strain every muscle and nerve towards the attainment 
 of more money and power, and thus it is that often we overwork our 
 selves, body and mind — become physical wrecks, not from the want of 
 an am[)le supply of food, but because from the mode of our living we 
 have not allowed it to nourish us properly. 
 
 I, therefore, wish to emphasize the great and, I may say, vital 
 importance that a knowledge of the requirements of the human body 
 and of the composition and character of our daily foods is to everyone 
 nowadays. In the first place we are confronted with the statement on 
 good authority that more suffer from overeatmg than from over-drinking, 
 though the number of victims of the latter vice, we must all admit, is 
 not small. Over-eating is a term used not onlv to designate the more 
 than sufificient use of simple, wholesome food but also to include the 
 taking in excessive quantities of rich and concentrated foods, most of 
 which may be called luxuries, and lastly, one-sided diets adopted either 
 from necessity or from mere fancy. Such diets are sooner or later 
 inevitably followed by disease or a disordered system. That dyspepsia 
 and allied ailments, especially on this side of the Atlantic, are very 
 prevalent, and that the same are due to art abnormal or c xcessive diet, 
 is well known, but that probably over fifty per cent, of the common dis- 
 orders now afflicting mankind are from the same causes, and which are 
 oreventable by a proper care of the body and a judicious diet, is cer 
 
V 
 
 tainly not widely recoyni:<ed by the la ty, thoii;;h the medical j^rofession 
 have repeatedly attested the truthfulness of the statemv-nt. 
 
 From a hygienic standpoint, therefore, we must admit the useful- 
 ness of that knowledge which tells of the true nu;ritive value of the 
 different foods and the amounts of them required to sustain health and 
 vigour —a knowledge that will enable us to use with discretion those 
 foods best suited to our wants and as a result experience mens sana in 
 corpote sano. 
 
 Cut the importance of the subject may be urged from another 
 aspect — the economic one. " Half the struggle of life is a struggle for 
 food," says Edward Atkinson, and though thid may appear an extreme 
 statement, reflection assures us of its truth. Evidence in its support is 
 supphed in abundance by our large cities where competition is rife and 
 the inhabitants are massed together. When the scourge of famine 
 overtakes a country, the misery and horrors which attend such a 
 catastrophe emphatically attest its accuracy. Surely, then, food-econ- 
 omy is a subject well worthy of study, lor from it governments and 
 individuals may learn how to obtain the most nutritious food for the 
 least outlay, and thus in limes of distress be enabled to alleviate much 
 suffering. But nearer home there seems to bj am|>lc room lor iniproving 
 our own condition in this matter of food-economy. I do n.t here refer 
 to that wilful waste of food in our homes, which I must designate a sin 
 against mankind, nor to that excessive use of food that engenders 
 disease. I wish, rather, to direct your attention to the study of con- 
 trasting the money value of foods with their nutritive value. Foi" by 
 such we shall be enabled to make choice of the most nutritious and 
 palatable viands at the least cost. Then, perhaps, while spending a little 
 less on our stomachs?, we should have somewhat more to ex|)end on 
 other and no less noble objects in life — the improvement of our 
 faculties and mental enjoyments — to say nothing of the noblest of all, 
 the benefitting of our fellow man in one or other of the many ways now 
 open to us. 
 
 And there is yet a third side to the question — that of pleasure. 
 This is, undoubtedly, a legitimate one for our consideration. The 
 pleasure of eating and drinking of the good things provided for us is 
 assuredly a right one, and one that has been so recognized from all 
 
 - ■^'v«c-Tm-'T.-~«"~'' .■ 
 
ha 
 
 
 times. But my subject is rather with foods themselves, and I must 
 hasten on, having briefly outlined the reas )n why! deem a kn(>\vltdge ^ 
 of what we ea; so important, so necessary as to warrant my impnssinn 
 upon you so urgently the value of its study 
 
 I^ is the food we eat that forms the tissues and developes the 
 heat and energy of our bodies. The body creates notlung, neither 
 matter or force. The physical life is dependent directly upon the 
 digested food, water, and the oxygen we breathe. The changes the 
 jood undergoes in the life functions are simply and truly tnnsforma- 
 tions. We shall therefore do well at the outset to consider briefly those 
 elements and compoimds that compose the body structure. 
 
 The Chkmical Hasis of thk Human Hodv. 
 
 Chemical analysis has proven that only fifteen, or at most seventeen, 
 of the elements enter into the composition of the tissues of the body. 
 In the following table, from Brubaker's Physiology, thc-y are enumt rated 
 together with the relative quantities in which they exist and the tissues 
 in which they are found. 
 
 Chemical Composition of the Hu.man Body. 
 
 O. H. C. are found in al! the tissues and 
 
 fluids of the body, without exception. 
 O. H. C. and N found in most of the fluids 
 
 and all the tissues^ except fat. 
 In fibrin, casein, albumen, gelatine of the 
 
 tissues, in sweat and urine. 
 In brain, saliva, blood and bones. 
 In bones and teeth, jn blood, saliva and 
 
 chyle. 
 In all the fluids of the body. 
 In muscles. 
 
 In bones, associated with calcium. 
 In the fluids and solid tissues. 
 With calcium in bones and teeth. 
 In blood corpuscles and in muscles. 
 In blood, bones and hair. 
 Probably in hair, bones and nails. ' 
 
 Oxygen, 
 
 72.00 
 
 Hydrogen, 
 
 U.IO 
 
 Nitrogen, 
 
 2.50 
 
 Carbon, 
 
 >35o. 
 
 Sulphur, 
 
 .147 
 
 Phosphorus, 
 
 115 
 
 Calcium, 
 
 1.30 
 
 Sodium, 
 
 •10 
 
 Potassium, 
 
 .026 
 
 Magnesium, 
 
 .001 
 
 Chlorine, 
 
 .085 
 
 Fluorine, 
 
 .080 
 
 Iron, 
 
 .01 
 
 Silicon 
 
 traces, 
 
 Manganese 
 
 traces, 
 
5 
 
 These elements do noi exist in the body in the free state, if we 
 except traces of unoombined Oxygen, Nitrogen and Hydrogen, but in 
 various combinations with one another forming exceedingly complex 
 compounds. These, for the s-ike of convenience, fall into two great 
 classes : -Okganic: and Inor«;anic, iliough the distit^ption is no longer 
 a strictly accurate one. The organic compounds may be considered 
 under the divisions, (</) Nitrogenous, (b) Non-nitrogenous, accord- 
 ing as to whether Nitrogen enters into their composition or not. Many 
 of the elements above cited are connnon to both the Organic and 
 Inorganic compounds. 
 
 The Nitrogenous compounds are the most numerous as to their 
 number as well as most fomplex as to their quantitative composition, 
 though they are made up of but four elements, Carbon, Hydrogen, 
 Nitrogen and CJarbon, with occasionally small amounts of Phosphorus 
 and Sulphur. We can here only mention certain large groups ot 
 these compounds. 
 
 Albuminoids or Proieids, a generic term including a number of 
 substances having the same percentage composition but different physical 
 properties. Sub-divisions comprise, (i) Native Albumens, of which the 
 white of egg is an exam[)le; (2) Globulins, chief among which is 
 Myosin, the organic b isis (A muscle ; (3) Derived Albumens, the casein 
 orcurd of milk and certain substances formed in the stomach during 
 digestion ; and (4) Peptones or Soluble Albuminoids, formed by the action 
 of the digestive fluids o^i food, and which pass into the blood to nourish 
 the body. Besides these there are the Gelatins found in hones, etc., 
 and certain other waste products formed by the_ life functions ot the 
 various organs of the body. 
 
 The Non-nitroge\ous organic compounds are made up entirely 
 of Carbon, Hydrogen and Oxygen. They consist of (a) Carbo-hydrates, 
 in which the Oxygen and Hydrogen are in proportion to form water ; 
 {b) Fats, richer in Carlson and Hydrogen than the Carbo-hydrates, {c) 
 Fatty acids and (d) Alcohols. 
 
 Carbo-hydrates, Sugar, Starch, are represented in comparatively 
 small quantities in the body, though found in many of the fluids and 
 
6 
 
 tissues. The forms of sugar are Glycogen of the liver, Lactose or sugar 
 of milk, Glucose (grape sugar) and Inosite of sugar of muscle. 
 
 Fats and Oils — Palmitin, Olein and Stearin. These are really salts 
 of the alcohol Glycerins with the fatty acids Palmitic, Oleic and Stearic. 
 The fat of the body is made up chiefly of Palmitin and Stearin (solids) 
 with small quantities of Olein (liquid). 
 
 The fatly acids require no special discussion here. Mention of 
 the three principal ones has already been made. These with Butyric 
 acid in milk and Propionic acid in sweat, exist in combination with 
 certain bases, e.g.. Potassium, Calcium and Sodium in various parts of 
 the body. 
 
 Alcohols : — Glycerine, a true . alcohol has already been spoken of 
 under ''fats;" it is also produced during digestion; C!holesterinc, a 
 crystallized uncombined alcohol, is present chiefly in bile. Ordinary 
 alcohol has been detected in the body — probably the result of a 
 fermentation in the digestive tr?.ct. Under normal conditions, however, 
 it is doubtful if it is produced. 
 
 Inorganic or Minkr.al Compounds. — The chief of these is 
 Water (Oxygen and Hydrogen), present to a very large extent in every 
 fluid and tissue. Its great importance and function will be spoken of 
 hter on. Calcium phosphate (phosphate of lime), another essential 
 compound, is the basis of bones and teeth, but also found in other 
 parts. Ciloridfc of Sodium (common salt) is to be- met with in all 
 tissues and fluids. Iron m minute quantities enters into the com- 
 position of haemoglobin, t^ - '-olouring matter of the blood. It is also 
 to be detected in many of the body tissues. 
 
 The foregoing outline may serve as an enumeration of the mole 
 important body substances. Their origin and physiological function 
 will bo discussed when speaking of the nutritive ingredients of foods 
 and the processes of digestion and assimilation. A knowledge of the 
 relative amounts of the chemical elements and of the compounds already 
 alluded to, as they exist in the body, will be found to be of 
 
 nterest and value. I, therefore, subjoin the following admirable tables 
 ..ompiled for the United States National Museum, Washington, by 
 
 Messrs. Welch and Pomeroy. 
 
m-' 
 
 WEIGHTS OK CHii*iaAL EI.KMF.NTS IN THE BODY OK 
 A MAN WtUaUNU I48 l.DS. 
 
 Oxygen 92.4 pounds 
 
 Carbon 31,3 " 
 
 Hydrogen' 14,6 '* 
 
 NitrV't-en 4.6 
 
 Calrium 
 
 Phosphorus 
 
 Potassium .* 
 
 Sulphur 
 
 Chlorine 
 
 Sodium 
 
 Mr'S^nesium 
 
 Iron 
 
 Fl lorine 
 
 Total 
 
 4.6 
 
 <i 
 
 2.8 
 
 It 
 
 14 
 
 ti 
 
 •34 
 
 <i 
 
 .24 
 
 « 
 
 .12 
 
 ti 
 
 .12 
 
 <t 
 
 .04 
 
 II 
 
 .02 
 
 
 .02 
 
 li 
 
 148.00 
 
 II 
 
 COMPOUNDS IN THE BODY OF A MAN WEIGHINO 
 148 POUNDS. 
 
 Water cjo.o pounds 
 
 Protein (vMbuuiinoids) 26.6 ", 
 
 Fats 23.0 " 
 
 Carbo hydrates (starch, sugar) i " 
 
 Mineral matters (inorganic) 8.3 " 
 
 Total 
 
 148.0 • 
 
 The Nutrients of Food. 
 
 Having learnt somewhat of the compounds of (be body and that 
 the latter is built up Ly the functions of the organs of the body from 
 the digested food, we may gc on to consider the composition of foods, 
 vegetable and animal. ■ In view of what has already been said we sha" 
 not be surprised '.o hear that the edible and nutritive portions consist, in 
 varying proportions, of those ingredients or compounds alre«idy consi- 
 dered, viz: Albuminoids, Carbo-hydrates, Fats and xMineraf matters 
 
 -'"^SSKSSSCSEiJSti.* 
 
 ■<*■ ; *»■! « *:»:»*- 
 
■n 
 
 i 
 
 1 
 
 1 
 
 '- 
 
 I 
 
 f 
 
 8 
 
 (including water). These are termed Nutrients, and the composition of 
 the three classes of organic compounds is roughly as follows : 
 
 Albuminoids. Fats. Carbo-hydrates. 
 
 Per cent. Per cent. Per cent. 
 
 Carbon 53.0 76.5 44.0 
 
 Hydrogen 7.0 12.0 6.0 
 
 Oxygen 24.0 1 1.5 50 o 
 
 Nitrogen 16.0 None None 
 
 loo.o 100.0 100.0 
 
 These Nutrients are by no means equally distributed throut^hogt 
 the food materials. The animal foods — meats and fish— vyhile very 
 rich in albuminoids and fats, possess but traces of the carbo-hydrates. 
 They rnay be considered, therefore, essentially nitrogenous. V'^egetable 
 foods as a rule contain a large percentage of Carbo-hydrates, starch 
 and sugar, and small quantities of albuminoids and fats, and conse- 
 quently may be considered as essentially ncn nitrogenous. An exception 
 to the latter is to be found in peas and beans, which contain a notable 
 amount of albuminoids. Very tat meats on the other hand, by reason 
 of the large amount of fat th(jy possess, cannot be considered as highly 
 nitrogenous. 
 
 This great distinction between these classes of foods is one 
 
 worth remembering as helping us to arrive at their true nutritive value. 
 
 To enable us to do this the better, however, we may now proceed to 
 
 state the physiological functions of these nutrients, whether they be 
 
 derived from animal or vegetable foods. For this purpose 1 shall take 
 
 the liberty of placing before you another chart from the National 
 
 Museum. 
 
 Uses of Food in the Body. 
 
 Food supplies the wants of the body in several ways. Food fur- 
 nishes : 
 
 1. The materials of which the body is made. 
 
 2. The materials to repair the wastes of the body and to protect 
 
 its tissues from being unduly consumed. 
 Food is consumed in the body as fuel to 
 
 3. Provide heat to keep it warm ; 
 
 4. Produce muscular and intellectual energy for the work it has to do 
 
9 
 
 Tne bjdy is built up and its wastes repaired by the nutrients. The 
 nutrients also serve as luel to warm the body and supply it with 
 strength. 
 
 Ways in which the nutrients are used in the body : 
 
 ''orm the nitrogenous basis of blood, muscle, sinew, 
 bone, skin, &c. 
 
 The alb 
 
 uminoia> [ 
 
 (Are changed in 
 Are consumed I 
 
 oJ food 
 
 to fats and carbo-hydrates, 
 for fuel. 
 
 The fats of f Are stored in the body as fats, 
 fo'-'d I Are consumed or fuel. 
 
 The rarf)o- f Are changed into fats, 
 hydrates of food\ Are consumed for fuel. 
 
 r Are transformed into the mineral matters of bone 
 The mineral | and other tissues, 
 
 matters ot food 1 . , . ,, 
 
 I Are used m various other ways. 
 
 This is a very instructive table, and it will be well before passing' 
 on to consider in more detail what it means. It emphatically tells us 
 in the first place that we cannot exist for any length of time on any one 
 class of nutrients — a fact amply proved by actual experiment No 
 one nutrient is a complete diet. A diet consisting entirely of albumi- 
 noids, or of carbo hydrates, or of fats, is an impossible one, though a 
 glance at the table shows that the albuminoids are more universal in their 
 functions that the other two nutrients. We shall learn later on some- 
 what of the prop^'r 'ratio in which they should be used in order to 
 preserve health. The tissues of the body are continually undergoing 
 disintegration, heat is being dissipated and muscular and intellectual 
 energy constantly ex|)cnded. Let us examine for a moment the different 
 classes of food as to their ]iower to supply these wants. 
 
 We have already said that animal foods— meats of all kinds and 
 fish — are principally nitrogenous. The albuminoids they contain are 
 often called flesh formers, because such go to form in the body the 
 muscle and the blood. They also possess more or less fat, which may 
 be laid up or converted into adipose tissue or used up in the production 
 of heat. 
 
 The vegetable foods consist largely of the carbo hydrates, and 
 
10 
 
 III 
 
 
 A1 
 
 I 
 
 cannot be said to assist in the formation of new tissue — muscle, blood, 
 &c., hut are of service, as fuel in developing the necessary heat and 
 energy. Of course, the fat^" they contain may be so used, or deposited 
 as such in the adipose tissues. 
 
 Water and mineral matters are common to both clashes of foods. 
 While both are absolutely necessary, they can scarcely be called nutrients. 
 Water is the universal solvent. Dependent upon its presence are the 
 processes of digestion and assimilation. The blood and lymph are 
 largely water, and by them the nutriiive matter is conveyed to every 
 part of the body. It also takes part in the elimination- of waste 
 products. Mineral matters, especially common salt and phosphate 
 of lime are required tor tissues and bones. " The salt in the blood 
 holds the albuminoids in solution, and by regulating the amount of water 
 in the blood corpuscles and the cellular elements of the tissues, preserves 
 their form and consistence." Phosphate of lime gives solidity to the 
 bones and teeth, and is also present in muscle, milk, &c. ' 
 
 Composition and Digkstibilitv of the Mohe Common Foods. 
 
 We may now consider the composition and digestibility of some of 
 the mote common foods. In the subjoined table, obtained from the 
 same source as the pieceding, the percentage indigestible, as well as the 
 total amount of each nutrient is given. It is a very instructive 
 chart and one that well deserves a careful study. It shows most clearly 
 the large amount of albuminoi'is, entirely digestible, in the animal loods 
 (meats and fish), and that in such, increased fat generally means 
 decreased water. This is exemplified in the case of fat pork. The carbo- 
 hydrates (starch and sugar) are practically absent in these foods. Eggs 
 we see to be a highly concentrated food, being rich in albuminoids and 
 fat, but containing no starch or sugar. Fish, generally speaking, is a 
 very nutritious food, being easy of digestion. Its value as a brain food 
 will be spoken of later on. Cod may he considered albuminoids and 
 water. Milk is shown to be a well balanced food — i.e. it contains all 
 the materials in good proportions and approaches most nearly the com- 
 position of a ' perfect food.' Its almost total digestibility makes it a 
 most important factor in the diet of the young and aged. It has been 
 found that boiling milk somewhat impairs its digestibility. Butter may 
 
11 
 
 Table showing composition and proportion of indigestible materials of 
 the more ordinary foods. 
 
 Ueef, rather lean . 
 iil •« rather fat. , 
 
 Mutton, fat 
 
 Pork, very fat . . . 
 
 Cod 
 
 Salmon 
 
 .Vf ackerel 
 
 Kggs 
 
 Milk 
 
 Butter 
 
 Aibutninoidii. 
 
 Fats, 
 
 Total. 
 
 2^.0 
 
 20.0 
 
 15.0 
 
 30 
 
 '5 o 
 
 22.0 
 
 i| 18.8 
 
 i! 13.4 
 
 I! 3'4 
 i I o 
 
 Cheese, whole milk li zj.i 
 
 Wheat, flour 11.6 
 
 ! 
 
 bread jj So 
 
 I 
 
 Oatmeal jl is o 
 
 Pease 
 
 Cornm^al 
 
 Siig.ir. 
 
 Poti»t(«es 
 Turnip.s. 
 
 I 
 
 5 
 22.9 
 
 1 9-1 
 
 I 
 
 i 03 
 I 2.0 
 1 .0 
 
 Carbo- 
 hyilrates. 
 
 1^ '; Total. 
 
 - £ : 
 
 0.0 i 
 o o I 
 
 1 
 ) 
 
 0.0 . 
 
 '■^^ ' Total. 
 
 Q 
 
 0.0 
 0.0 
 
 0.0 
 2. I 
 
 1 .2 
 
 3-2 
 I .2 
 
 03 
 
 9.0 
 19 o 
 40.0 
 So. 5 
 
 I.O 
 
 14-3 
 8.2 
 
 II. 8 
 3-7 
 
 87.5 
 
 3? 5 
 0.8 
 
 19 
 SO 
 
 1.8 
 
 3S 
 0.0 
 02 
 o 2 
 
 0.9 
 I 
 
 0.0 
 9 'I 0.0 
 0.0 
 0.0 
 0.0 
 0.0 
 
 -i 1; 
 
 w 
 
 1/ 
 
 
 ■ii 
 
 0.0 
 
 0.0 
 
 0.9 
 
 0.0 I 
 
 I 
 
 0.0 ; 
 
 00 ! 
 
 4 ! o.y 
 
 I i! 4-8 
 
 0.0 0.0 , 
 0.0 
 
 I 
 
 OS 
 
 9 ;, 2-3 
 
 I 
 
 ; 72-2 
 
 I 55-5 
 69.0 
 
 57-8 
 71.0 
 
 96.7 
 
 II 
 
 |l 21.3 
 i 6-9 
 
 0.0 
 
 0.0 
 1.8 
 
 1-3 
 1 .0 
 1.0 
 6.5 
 15 
 1-7 
 "4 
 1 .0 
 0.7 
 3.0 
 
 3 9 
 0.4 
 
 0.6 i 1 .0 
 
 . ... II 1.0 
 
 2.3 j 
 0.0 j 
 1.6 i 
 
 1-3 
 
 i| 
 
 2-5 
 
 1.6 
 0.8 
 1 .0 
 0.7 
 
 
 66.7 
 60.0 
 44.0 
 10. o 
 82.5 
 62.0 
 71.6 
 73 •« 
 87.4 
 9.0 
 31.2 
 15.0 
 
 32 -7 
 10. o 
 
 'S-o 
 
 US 
 
 2.2 
 
 75 S 
 91 .2 
 
 ■wwsiWMr-- 
 
Ml 
 
 13 
 
 i. 
 
 be considered pure fat, which is easy of digestion and assimilation i( 
 the condition of the stomach be normal and too much be not taken. 
 Cheese is a highly nitrogenous and exceedingly valuable food. It not 
 only is easily digested but also assists in the digestion of other foods. 
 Its price, when we consider these important desiderata, recommends it 
 for more extensive use than it at^ present enjoys. 
 
 The vegetable foods are characterized by low albuminoids and high 
 carbo-hydrates. The amount of fat in most of them is small, and need 
 hardly be taken into account as a nutrient. Peas and beans (fruit of the 
 Leguminosce) stand out as exceptions in containing large percentages 
 of albuminoids. Oatmeal also more closely approximates animal foods 
 than any of the other cereals. The starch and sugar of vegetable foods 
 , is as a rule very digestible. The vegetables proper consist largely of 
 starch, or allied substances, and water. Potatoes, cabbage and many 
 other vegetables are also valuable for the mineral salts they contain. 
 Asparagus, lettuce, celery and some others contain but little nutritive 
 irjitter, bu*: play a very im[)ortan; hygienic role, aiding the digestion 
 of other viands, diluting the more concentrated foods, and thus render- 
 ing them more easily assimilable ; the salts and active principles many 
 of them contain have a beneficial and medicinal effect on the sys- 
 tem. Vegetables must form a large part of every wholesome diet. 
 Fruits are largely water, and are divided into {u) Sweet, in which sugar 
 predominates when ripe ; (/•) A.:id, containing tartaric and citric acid, 
 generally refre-shing and giving a he.dthy tone to the organs; (c) Starchy; 
 and (i/) Oily, the esstnti il oils in which give the peculiar flavour. 
 Fruits, though having a low nutritive value, are, when ripe, easy of 
 digestion. The pectose L.f green fruit is indigestible. This as the fruit 
 ripens turns to pectin, akin to sugar, which, as before stated, is easily 
 digested. The odour and flavour of fruits, due as before mentioned to 
 oil> and vol.itile ethers, chiefly abundant in the pericarj), seem to 
 enhance their palatability. 
 
 Here a word may be said of a large class of substances which 
 act rather as stimulants than nutrients. Tea, coffee, spices and alcohol 
 come under this category. They act as appetisers, and in moderation 
 as useful and proper excitants of the digestive organs, especially in 
 cases of enfeebled digestion. 
 
13 
 
 Amounts of the Nutrients Required. 
 
 The quantity and kind of food eaten must depend largely on 
 the age, the weight, and the Wind and amount of work of the in- 
 dividual, taking into consideration the climate and the peculiar char- 
 acteristics of the person's digestion — a most important factor. The 
 amount of food required per diem by the body is measured by the 
 amount of carbon and nitrogen eliminated daily from the system. 
 These represent the final and waste products of the food compounds. 
 The weight of carbon excreted by a healthy person in one form or 
 another doing a fair amount of work is about fifteen times heavier than 
 that of the nitrogen. The carbon daily eliminated is about 4,600 
 grains, the nitrogen about 300 grains. These numbers are the results 
 of many experiments, but for many reasons are only approximate. In 
 order to retain health it is necessary to preserve as closely as possible 
 t'lis ratio in our diet, for not only do we wish to avoid an excess or 
 lack of food, but also the excess or lack of any cj^ne ingredient. If we 
 supply the nitrogen (Albuminoids) altogether from vegetable' foods, 
 such a large quantity has to be consumed that there would be a large 
 excess of carbon — a state of affairs seriously affecting the health. On 
 the other hand, if the required amount of carbon is to be obtained 
 from an exclusive meat diet, about four times as much nitrogen as 
 needed would be furnished. This would seriously impair the digestion 
 and be apt to induce disease. 
 
 AsT have before emphasized, no one class of nutrients is in itself a 
 complete food, and it is only when they are in proper proportions that a 
 healthy and vigorous system can be maintained. Though there is 
 strong tendency in the system to eliminate any excess of food, yet, is 
 I have pointed out before, too much food acts deleteriously. The 
 habitual use of large quantities of meat and albuminous foods induces 
 a diseased condition of the liver, gout, itc, while excessive amounts of 
 the fats, starch and sugar cause obesity and dyspepsia. 
 
 Professor Ranke found that when doing no muscular work, his 
 weight was mamtained with the following per day. 
 
 Albuminoids, 3.5 ozs. ; Fats, 3.5 ozs. ; Carbo-hydrates, 8.5 ozs. 
 Professor Voit, an eminent German scientist, gives the following 
 
^i^H ' ^J^-^^S - ^'jA-i '' ^ ■' '> J^. 'i L'. ' [ 
 
 '"■ir'-r iii '-'TT rT'ir a~"r7rr-ih inti y i« i i irrr^^ 
 
 hi 
 
 U ! 
 
 I 
 
 14 
 
 amour iS per day for an adult doing an ordinary day's (muscular) work, 
 supposing neither to gain nor loose weight. 
 
 Albuminoids, 4.2 ozs.; Fats, 2 ozs.; Carbo-hydrates, 17.6 ozs. 
 Professor W. O. Atwater, of Washington, U.S.A., who has written 
 a splendid series of articles in the "Century" for 1887, on the subject 
 of foods, tn which I am largely indebted for material in these lectures, 
 estimates that an average man doing muscular work requires — 
 
 For moderate work, Albuminoids, 4.4 ozs.; Fats, 4.4 ozs.; Carbo- 
 hydrates, 14.4 ozs. 
 
 For bard work, Albuminoids, 5.2 ozs.; Fats, 4.4 ozs.; Carbo- 
 hydrates, 14.4 ozs. 
 
 Professor Parkes says that the food required for a healthy adult is : 
 For laborious occupation, Albuminoids, 6 to 7 oz; Fats, 3.5 to 4.5 oz; 
 Carbo-hydrates, 16 to 18 oz; Salts, 1.2 to 1.5 oz. 
 
 At rest. Albuminoids, 2.5 oz; Fat, i oz; Carbo-hydrates, 12 oz; 
 Salts, .5 oz. 
 
 The harder the work the more nitrogenous (a)huminoids) should 
 the diet be. 
 
 The htat of the body in order to be maintained necessitates the com- 
 bustion of a large proportion of the food, probably about ^q of it. This 
 heat, together with the work expended internally in the functions of the 
 heart, respiration, &c., and the external muscular action in locomotion 
 and other voluntary work, represent an amount of energy calculated at 
 about 3,400 foot-tons, i.e., the force required to raise 3,400 tons i foot 
 high. The heat of the body represents in amount that required to raise 
 48.4 lbs. from the freezing to the boiling point, or in mechanical power 
 would be sufficient to raise 150 lbs. through a vertical height of 8^ 
 miles. All this must be provided for by food and oxygen before makiti 
 any demands on the system for muscular or brain labour. 
 
 Fish as a Brain Food. 
 
 I may here allude very briefly to the common, but erroneous, opinion 
 that brain work requires or is benefitted by a liberal fish diet. This has 
 arisen from statements made to the effect that thought and brain work 
 in general used up a large quantity of phosphorus, and secondly, that 
 fish supplied in abundance this element. Neither of these assertions 
 appears on r ,vesti"ation to be true. The brain tissue consumed by 
 
15 
 
 mental activity contains no more phosphorus than thit of other parts of 
 the body — not so much as the bones and teeih. Fish does not furnish 
 this ei-fment more abundantly than other animal foods. Good head 
 work like good hand woric requires a good digestion, and as fish is eas'ly 
 assimilated it may, for this very reason, be found of great value to 
 brain workers, especially if such do not take sufficient muscular exercise 
 to induce a vigorous digestion. ^ 
 
 Before bringing these lectures to a close I wish to give you an 
 outline of the process of digestion, the changes that take place in 
 cooking food, and a few practical remarks drawn from a consideration 
 of the whole subject. 
 
 Digestion. 
 
 Mastication or trituration of the food in the mouth serves by a 
 thorough division of the material to present a greater surface to the 
 solvent action of the digestive fluids. An increased digestion is the 
 result. Sahva, secreted by certain glands of the mouth, softens and 
 moistens the food and converts the insoluble starch into soluble 
 sugar. In this reaction the active principle is Ptyaline. 
 
 The gastric juice, the secretion of the true peptic glands of the 
 stomach, has a physical and chemical action. It dissolves and disin- 
 tegrates the food, reducing it to a liquid condition, and converts tne 
 albuminoids into peptones, which are assimilated by the blood. Its 
 composition is : — 
 
 Water 97-5 
 
 Pepsin 1.5 
 
 Hydrochloric acid .5 
 
 Salts .5 
 
 * 100. o 
 
 It has an ncid reaction. 
 
 The intestinal digestion is promoted by the pancreatic juice, which 
 has an alkaline reaction. It has a fourfold function : — 
 (i) Converting starch into sugar. 
 
 (2) Converting albuminoids into peptones. 
 
 (3) The emulsification of fats. 
 
 (4) Conversion of cane sugar into grape sugar. 
 
miWriiiMmMdiiyadi* 
 
 16 
 
 Bile, formed in the hepatic cells, assists in the tniulsificaiion of fats 
 and promotes their absorption and stimulates the secretions ef the 
 intestinal plands. It also serves to prevent putrefactive changes in the 
 food. The digested food or chyme is absorbed by the blood as 
 the food passes through the intestines, the undigested portion entering 
 the larj:;e intestines. 
 
 The Chemistry of Cooking. 
 
 The changes induced by cooking are manifold, some increasing, 
 others decreasing the digestibility of the food, while others only serve 
 to render the same more tasteful by the production of certain substan- 
 ces which pleasantly excite the palate. 
 
 Meats are more readily digested when "underdone" than well 
 cooked, though undoubtedly very tough meat by its disintegration is 
 rendered more tender and easy of mastication by the process. Certain 
 empyreumatic substances are developed by roasting And boiling meals 
 which give agreeable taste and savoury odours. These act rather as 
 stimulants than nutrients, and render the. food more palatable than in 
 the uncooked condition. Roast beef, beef tea and soups owe their 
 piquancy to these compounds. Eggs and milk are rendered less 
 digestible by cooking, for the reason that coagulated albumen is not 
 readily acted upon by the digestive fluids. 
 
 On the other hand, most vegetable foods require cooking to in^ 
 crease their digestibility. The cells containing the staich in the raw 
 material have walls of cellulose, difficult of digestion. By cooking, this 
 cellulose is softened and the starch grains are burst. The contents then 
 are more completely exposed to the digestive fluids. 
 
 In summing up I would offer the following remarks and deductions. 
 Their importance, I think, merits your consideration. 
 
 I. That in the choice of vfands care should be taken that the diet 
 consists of both vegetable and animal foods. The proportion of 
 nutrients may roughly be stated at three times the weight of carbo- 
 hydrates to equal weigh*s of fats and albuminoids. Excess of any one 
 nutrient is likely to be injurious to health. 
 
 It would seem that nature teaches what science cor^^rms — a 
 proper combination of materials. The Irishman with his potatoes 
 (carbo-hydrates) and buttermilk (albuminoids), the Englishman with 
 
17 
 
 his bread and cheese (carbohydrates, fat and albuminoids), and many 
 others, excmjjh'fy this inference. 
 
 2. Starch, sugar and fats are essentially heat and energy produ<:ers. 
 As heat producers fats are about 2 j-^ times more valuable than carbo- 
 hydrates. In cold climates we find the inhabitants existing largely on 
 fatty foods. Esquimaux and lumbermen are notable examples. 
 
 The albuminoids are the most costly of all the nutncnts. While 
 performing to some extent the functions just mentioned, they have for their 
 chief office that of building up the tissues of the body and ropairing 
 the waste continually going on. The albuminoids cannot be replaced 
 in the diet by any other material. 
 
 3. Fruits and many vegetables while not rich in nutritive material 
 should form a large part of the diet, as they assist in digestion and, 
 acting medicinally, give a healthy tone to the system. Salads of lettuce, 
 celery and beets, if not too rich, have a cooling and refreshing effect. 
 
 4. Condiments and stimulants are often desirable as appetisers 
 and in moderate amounts excite the flow^ of the digestive fluids, and 
 thus aid digestion. Excess of alcohol, tea and certain other articles of 
 this class is well known to have injurious physiological action. 
 
 5. Cooking, while, as a rule, rendering the animal foods rather less 
 digestible, makes vegetable foods more fit for consumption. 
 
 6. Mastication should be thorough in order that the food may be 
 well mixed with saliva, and tor this purpose slow eating is to be 
 recommended. 
 
 7. The process of digestion is a continuous one. Active work 
 retards somewhat the digestion of a heavy meal, and such should, 
 therefore, be taken rather after the work of the day than during it. The 
 times of meals must largely be regulated by the amount and kind of 
 work. It is better to eat a little and often than to overload the dit^estive 
 apparatus at any one meal. Though the digestive process is not so 
 vigorous during sleep as in ihe day time, light refreshment is to be 
 recommended before retiring — the stomach thereby is kept from being 
 totally void of food in the morning. To those who are not robust eaters 
 this advice is more particularly given. 
 
 8. The blooi which conveys the digested food to every part of the 
 body is largely water On this account and because all the tissues contain 
 
^SSISmS. 
 
 ^^^SSI^BnB 
 
 « 
 
 
 18 
 
 a large amount of this compound, and the waste ol the body is partially 
 eliminated in a fluid form, it is necessary that as such, or under the 
 guise of some drink, a considerable quantity of water be daily taken. 
 Very cold water lowers the temperature of the stomach, retarding diges- 
 tion. In excess, water dilutes detrimentally the gastric juice. The 
 aged, therefore, and those whose digestion is not vigorous should avoid 
 too much water, especially of A low temperature. For such, a light wine 
 or other stimulant in moderation is undoubtedly beneficial. In drinking 
 as in eating the appetite is a safe guide. As a rule it is wise not to satiate 
 the appetite for solids or fluids. The old adage " Rise with an appetite 
 and you will always sit down with one," is a wise one. 
 
 9. Pastry and sweetmeats. Hot rich pastry and cake are exces- 
 sively indigestible, and in no sense can be considered as complete 
 foods. They should be sparingly eaten, if at all. Excess of sugar, as 
 in sweetmeats, deranges digestion. 
 
 10. Many "made dishes" are very rich and concentrated, and can 
 scarcely be considered as having a place in a wholesome diet. 
 
 I !> 
 
 I it;