On food : its varieties, chemical composition, nutritive value, comparative digestibility, physiological functions and uses, preparation, culinary treatment, preservation, adulteration, etc. being the substance of four cantor lectures delivered before the society for the encouragement of arts, manufactures, and commerce, in the months of January and February, 1868

Front matter

Med

7"7 m

*

Contents

LECTURE II.

COMPARATIVE DIGESTIBILITY OF FOODS. FUNCTIONS OF DIFFERENT

FOODS.

Preface

JT is necessary to inform the reader that the following Le(5tures were not originally intended for publication, but were delivered, from very brief notes, before the Society of Arts — the subjecft having been sele(5ted by the Council of the Society. Finding, however, that the ledtures have unexpectedly received a large share of attention, and have been printed verbatim in several English and American Journals, and that American and French editions of them were in course of publication, I have been induced to revise them more carefully, and to place them in an amended form before the public. All the tables, therefore, have been re-calculated, in order that the numbers might be in accordance with the most approved analytical data.

In dealing, however, with so large a subject as the economy of food, it was difficult, on the one hand, to

X

PREFACE.

seleft points of interest, and, on the other, to treat them with sufficient clearness within the narrow limits of a short course of four lectures ; and therefore, after due consideration, I thought it best to give a brief popular account of the different varieties of human food and their dietetical values ; and to point out the relation which exists between food and labour ; and to explain the principles involved in the proper construction of dietaries. Relying upon the experimental data of Dr. Frankland and others respecting the thermotic power of different kinds of food, and the equivalent of that power in mechanical work, as ascertained by the investigations of Mayer and of Joule, * I have endeavoured to express the labour value of most of the commoner articles of diet. Looking, also, at the aCtual amount of work performed by an ordinary individual, with a certain fixed diet, it has been easy to determine the opus vitale or internal work of the human body in performing the physiological functions of respiration, circulation, nutrition, &c.

In the construction of dietaries I have depended largely upon the enquiries of Dr. Edward Smith, and

* According to Joule, the heat necessary to raise i Ih. of water i° of F., is capable of lifting 772 lbs. one foot high.

XI of Dr. Lyon Playfair — the former having diredl;ed his attention to the dietaries of the low-fed operatives of this kingdom, and the latter to the dietaries of well-fed artisans and others. From these data I have been able to construdf standard proportions of food for idleness and for labour. The importance of this part of the subjecft cannot be over-rated ; for it not only concerns the dietetical wants of the community, but it also affecfts the dietetical treatment of our paupers and criminals. At present, the dietaries of the prison and the workhouse, are construaed upon the most capricious principles, and hence there is often either a wasteful excess of food, or a serious deficiency of it. As a rule, the criminals of this country are over-fed, and it is an important question— how much of the turbulence of the jail is referable to the unemployed and even explosive force of a too liberal diet. On the other hand, the pauper is frequently under-fed; and the consequences of it are a lowering of the vital powers, and a general debility of the muscular system. These are important social questions, and must ere long receive the attention they deserve.

The funaions of the several constituents of food have been examined from new points of view ; and the

Xll

PREFACE.

opinions of Liebig, as to the special force-producing or motive power of nitrogenous food have been carefully considered. This has become necessary from the circumstance that they have been recently tested by adtual experiment, and it has been found, that the muscular energies of the body may be sustained, and considerable labour performed, with a purely non-nitrogenous diet. It is even probable that the thermotic power of food is at all times the true exponent of its mechanical or motive power, and that this is quite independent of its nitrogenous or non-nitrogenous nature ; although it is evident from chemical considerations that the carbo-hydrogens, as fat, sugar, and farinaceous matters, are far more sustaining, in a thermotic sense, than nitrogenous foods, whose functions are perhaps chiefly to repair the waste of tissues. It must be admitted, however, that this part of the subject is still incomplete, and requires much experimental investigation before it can be satisfadtorily determined.

As regards the culinary and other treatment of food, as well as the preservation of it, I have endeavoured not only to discuss the general principles of the matter, but also to give, especially under the last head, very copious illustrations of pradtice. I have likewise

PREFACE.

Xlll described the circumstances which render food unwholesome, and have briefly adverted to its principal adulterations. In all cases, however, the numerous subjedts have been so treated as to condense the fadts as closely as possible, in order that they might be brought within the limited space of a very short course of ledtures ; and I submit this to the reader, not merely as a claim upon his indulgence, but as an excuse for many evident imperfedtions and shortcomings.

London, December, i86g.

THE CANTOR LECTURES.

ON FOOD.

LECTURE I.

VARIETIES OF FOOD — THEIR CHEMICAL COMPOSITION AND NUTRITIVE VALUE.

HE economy of food, in its fullest signification, is a matter of national importance ; for the political influence of a nation is as much dependent upon the muscular strength of the people as upon their intelligence and commercial industry ; and this strength is wholly referable to a right use and proper distribution of food.

We perceive this not merely in the calamities of acStual want, as in the fevers of famine, but also in the less prominent, but equally significant, decline of health in times of only partial distress, when the vigour and energy of the poorer part of the population are so reduced as to render them an easy prey to disease. In fa(5t, the experience of our

B

On Food.

public hospitals too often elicits the fadl that the wasted power of the patient has been the advent of incurable disorder. Nor is this all ; for, as Mr. Simon observes — “ Long before insufficiency of diet is a matter of hygienic concern, long before the physiologist would think of counting the grains of nitrogen and carbon which intervene between life and starvation, the household will have been utterly destitute of material comfort; clothing and fuel will have been scantier than food ; against inclemencies of weather there will have been no adequate prote(51;ion ; dwelling-space will have been stinted to the degree in which over-crowding produces or increases disease ; the home will be where shelter can be cheapest bought, where sanitary appliances are least considered, and where cleanliness is almost impossible.” And all this distress falls heaviest upon those who are least able to bear it — the mother and her children; for the father, to be able to work, even lightly, must eat, and thus the others are the largest sufferers. Bad, however, as the immediate consequences are, they are nothing in comparison to the remote — the sickly race that comes of want.

In examining, therefore, this question of the economy of food, we must not only look at the nutritive value of different articles of diet, but we must also consider how food can be best distributed and utilised.

To-day we will investigate the principal varieties of food, and ascertain their peculiar qualities and dietetical

Ntitritive Standards.

values. For this purpose it would be a great advantage to have some simple standard for comparison, but this is avowedly a difficult matter, for if we compare foods according to the proportions of their principal constituents, as the albuminous, starchy, saccharine, and saline — we shall find that the relative quantities vary to such a degree as to make the comparison almost useless ; and if we fix our attention on one of these constituents— the nitrogenous, for example — and make it the exponent of nutritive value, we get into the difficulty of either overloading the equivalent with a krge amount of carbonaceous material, or having it deficient therein. If, for instance, we desire to know the quantities of different foods which would furnish the 1220 grains of nitrogenous matter required by a man in his daily diet, we should find that the following are the proportions : —

Table I.

Proportions of Different Foods Required to Yield 1220 Grains of

Nitrogenous Matter.

Skim cheese .

Grains.

Pounds.

0*4

Lean meat ....

White fish ....

1*0

Fat meat . . . ,

1*3

Fat bacon ....

12,449

1-8

Bread

15,062

Rice

19.365

2’8

New milk ....

29.756

4*2

Potatoes ....

58,095

8-3

Parsnips or turnips .

111,000

15*9

Beer or porter .

1,110,000

158-6

In this manner tables have been construfted of the nutritive values of food, and I show you one of them.

Table II.

Nutritive equivalents — calctilated aceording to the amounts of Nitrogen in the Dry Substances ; Human milk being loo: —

Vegetable.

Rice . . .

Oats .

Potatoes . .

White bread

Maize . .

Black bread

Rye . . .

Peas . . .

Radish . .

Lentils .

Wheat . .

Haricots

Barley ! .

Beans

Animal.

Human milk .

Lamb .

Cow’s milk

White of egg

Yolk of egg

Lobster .

Oysters .

Skate . . .

Cheese .

Veal . . .

Beef .

Mussel . . .

Pork . . .

Ox-liver

Turbot

Pigeon .

Ham .

Mutton .

Herring . .

Salmon . .

I hardly need say that comparisons of this description are of little pradticalvalue, for they furnish no indication of the digestive labour required to utilise the products ; besides which, we are far from being assured, at the present time, that the nitrogenous elements of our foods are the most important.

Nutritive Values of Food

In framing, therefore, a table of alimentary equivalents, regard must be paid to all the constituents, and this I have endeavoured to do in Table No. 3, wherein I have shown the percentage proportions of nitrogenous and carbonaceous matters ; but here again the adtual value of the several carbonaceous compounds is very different ; for, although the fattening and respiratory powers of starch, gum, sugar, and pedtin are perhaps nearly the same, yet the power of fat is about 2*5 times as great as that of sugar ; and this must be considered, irrespective of other functions of fat, in estimating the value of carbonaceous food. I have therefore given the proportions of carbonaceous matters when calculated as starch.

Another method of determining the values of food, is by estimating the proportions of nitrogen and carbon in them, and comparing them with the proportions required in a standard diet.

Judging from the minimum quantities of food which an ordinary individual is capable of existing on, without suffering in health, it would seem that about 3888 grains of carbon and 181 grains of nitrogen are required in his daily diet. These proportions have been determined from a large number of observations, as by those of Dr. Lyon Playfair, in his inquiries into the dietaries of hospitals, prisons, and workhouses, and by those of Dr. Edward Smith, in his examination of the amounts of food which the Lancashire operatives were capable of living

Table III. — Nuiriiivc Values of Food.

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Nutritive Values of Food.

on during the cotton famine, and also by his inquiries into the dietaries of in-door labourers. The proportions which Dr. Smith gives as a famine or barely sustaining diet, are the following: —

Carbon (grains).

Nitrogen (grains).

Adult woman . .

Adult man ....

Average adult . . .

These proportions are

contained in

2lbs., and in

2lbs. 40ZS. of bread ; and they closely accord with another set of fadts, derived from an examination of the amounts of carbon and nitrogen exhaled and secreted from the body during health and idleness.

Taking these numbers, therefore, as the exponents of the nutritive values of food, we are able to construdt the following table : —

Table IV. — Nutritive Values of Food.

Grs. per Pound. Grs. for One Weekly Cost of

Value Penny. Famine Diet for

Carbon.

Nitrogen.

il.

Carbon.

Nitrogen.

Carbon.

d.

Nitrogen.

d.

Split peas. .

I io'6

5’4

Indian meal

I

9'5

Il’I

Barley meal

I

II‘2

19-6

Rye meal . .

li

13-3

19-3

Seconds flour . .

li

15-9

17-3

Oatmeal . .

20-3

Bakers’ bread . .

If

21'7

22‘5

Pearl barley

21-6

29'5

Rice

21-0

Potatoes . .

of

30-2

Turnips of

5I-I

Green vegetables of

47’5

Carrots

I

56-5

Parsnips . .

I

51-8

IIO-8

Sugar

—

—

48-6

—

G(<s. I'ER PoyND. Grs. for One

Value Penny.

A ^ PER

Pound.

Weekly Cost of Famine Diet for

Carbon.

Nitrogen.

d.

Carbon.

Nitrogen.

Carbon.

d.

Nitroge

d.

Treacle

—

I

—

—

Buttermilk..

oi

15-1

Whey . , . .

Oi

45-8

25-6

Skimmed milk . .

X

30 9

New milk . .

60-5

Skim cheese

44*2

8-3

Cheddar cheese

68-6

Bullocks’ liver . .

92-2

19-6

Mutton

75‘5

Beef

57-8

Fat pork . .

48-8

88 7

Dry bacon. .