Chapter V: Section II: Composition of Organic Substances

_Elements of Organic Bodies._--The number of distinct kinds of substances--each distinguishable from all the others by the peculiarity of its properties, taken as a whole--is exceedingly great, yet all these substances are resolvable into a very small number of bodies. As an illustration, I shall take a well-known substance, common green copperas, or, as the chemists term it, protosulphate of iron. By submitting this compound to the process termed chemical analysis, two other kinds of matter may be obtained from it, namely, oxide of iron and oil of vitrol, or sulphuric acid. If we continued this process--if we submitted the acid and the oxide to analysis--we could separate the former into sulphur and oxygen, and the latter into iron and oxygen. Now, by these means we could demonstrate the compound nature of copperas; we could prove that it was _proximately_ composed of sulphuric acid and oxide of iron; and, _ultimately_, of iron, sulphur, and oxygen.

Iron, sulphur, and oxygen, are elementary, or simple bodies. They cannot be decomposed; they cannot be analysed. Torture them as we will in our crucibles; expose them as we please to the highest temperature of a wind furnace, or to the more intense heat evolved by a powerful galvanic battery; subject them to the influence of any agent, or force, or process we may choose, and still they will yield nothing but iron, sulphur, and oxygen: hence these undecomposable bodies are regarded as _elements_, or simple substances. So far as our knowledge extends, there are about sixty-six of these undecomposable bodies, of which about one half occurs in but exceedingly minute quantities, and a considerable number of the others exists in comparatively small amounts. As by far the greater proportion of compounds is made up of two or more of about a dozen elementary bodies, it would at first sight appear as if the distinct kinds of compounds which exist, or which may be called into existence by the chemist, must be limited to, at most, a realisable number; but the fact is there is no practical limit to the variety of substances which may be artificially formed. Every difference in the mode of the arrangement of the constituent atoms of a compound, causes its metamorphosis into another kind of substance. To prove that the number of these changes is bounded by no narrow limits, I need but refer to the rules of Permutation, which demonstrate that twelve letters of the alphabet may be arranged in no fewer than 479,000,000 different ways.[1] The elements are the letters of Nature's alphabet, their compounds are the words of the language of Creation. The combinations of sounds and of signs which express the ideas and sensations of man may be limited to millions; but numberless are the hieroglyphs by which the Divine wisdom and beneficence is inscribed on the pages of the magnificent volume of Nature.

Of the sixty-six elementary bodies, not more than a dozen occur commonly in animal and vegetable substances; these are Oxygen, Hydrogen, Nitrogen, Carbon, Sulphur, Phosphorus, Chlorine, Silicium, Potassium, Sodium, Calcium, Magnesium, and Iron. In addition to these, Iodine, and sometimes Bromine, are found in plants which grow in or near the sea; and the former element has also been detected in some of the lower animals, and in land plants. Manganese, Lithium, Caesium, Rubidium, and a few others of the simple bodies, occasionally occur in plants and animals, but I believe their presence therein is always accidental.

_Proximate Composition of Animal Substances._--The differences between vegetable and animal substances are often more apparent than real. Indeed many of the more important of these substances are almost identical in composition. The albumen which coagulates when the juices of vegetables are boiled, is identical with the albumen of the white of eggs; the fibrine of wheat is in no respect chemically different from the fibrine, or clot, of the blood; and, lastly, the legumine, or _vegetable caseine_, of peas is almost indistinguishable from the curd of milk, or _animal caseine_. But not only has chemical research demonstrated the identity of the albumen, fibrine, and caseine of vegetables with three of the more important constituents of animals, it has gone a step further, and proved that they differ from each other in but a few unimportant respects. They are unquestionably convertible into each other[2] within the animal organism; and their functions, as elements of nutrition, are almost, if not quite, identical.

Exclusive of the blood, which contains the elements of every part of the body, the animal organism is composed of three distinct classes of substances--namely, _nitrogenous_, _non-nitrogenous_, and _mineral_. All of these constituents, or substances capable of being converted into them, must exist in the food. Certain articles, for example, milk, contains all of them; but in others, for instance, butter, only one of these substances is found. The nitrogenous part of the body embraces the muscles, or lean flesh, the gelatine of the bones, and the skin and its appendages--such as hair and horns; the non-nitrogenous constituents are its fat and oil; and its mineral matter is found chiefly in the bony framework. These constituents are not, however, isolated: the mineral matter, no doubt, accumulates in certain parts, but in small quantities it is found in every portion of the body; and although the fat forms a distinct tissue, the muscles of the leanest animal are never free from a sensible proportion of it.

Albumen, fibrine, and caseine are the principal nitrogenous constituents of food, and as they are employed in the reparation of the nitrogenous tissues of the animal body, they have been termed _flesh-formers_.

The fat and oil of animals are derived either from vegetable oil and fat, or from some such substance as starch or sugar. The constituents of food which form fat are termed _fat-formers_, and sometimes _heat-givers_ or _respiratory elements_, from the notion that their slow combustion in the animal body is the chief cause of its high temperature.

The mineral elements of the body are furnished principally by the varieties of food which contain nitrogen. The whey of milk is rich in them; but they do not exist in pure butter, in starch, or in sugar.

Fat is a much more abundant constituent of the animal body than is generally supposed, That this substance should constitute the greater portion of the weight of an obese pig seems probable enough; but few are aware that even in a lean sheep there is 50 per cent. more fat than lean.

For a very accurate knowledge of the relative proportions of the fatty, nitrogenous, and mineral constituents of the carcasses of animals used as human food, we are indebted to Messrs. Lawes and Gilbert. Before these investigators turned their attention to this subject, it had scarcely attracted the notice of scientific men; but a notion appears to have been current, amongst non-scientific people, at least, that in all, save the fattest animals, the lean flesh greatly preponderated over the fat. That this idea was unsustained by a foundation of fact, has been clearly proved by the results of an investigation[3] undertaken a few years ago by Messrs. Lawes and Gilbert--an investigation which I cannot avoid characterising as one of the most laborious and apparently trustworthy on record. The mere statement of the results of this inquiry occupies 187 pages of one of the huge volumes of the Transactions of the Royal Society--a fact which best indicates the immensity of the labour which these gentlemen imposed upon themselves, and which, independently of their other and numerous contributions to scientific agriculture, entitles their names to most honourable mention in the annals of science.

I shall now briefly advert to a few of the more important facts established by Lawes and Gilbert. From a large number of oxen, sheep, and pigs, on which feeding experiments were being conducted, ten individuals were selected. These were, a fat calf, a half-fat ox, a moderately fat ox, a fat lamb, a store sheep, a half-fat old sheep, a fat sheep, a very fat sheep, a store pig, and a fat pig. These animals were killed, and the different organs and parts of their bodies were separately weighed and analysed. The results were, that, with the exception of the calf, all the animals contained, respectively, more fat than lean. The fat ox and the fat lamb contained each three times as much fat as lean flesh, and the proportion of the fatty matters to the nitrogenous constituents of the carcass of the very fat sheep was as 4 to 1. In the pig the fat greatly preponderated over the lean; the store pig containing three times as much, and the fat pig five times as much fat as lean.

That part of the animal which is consumed as food by man, is termed the _carcass_ by the butcher, and contains by far the greater portion of the fat of the animal. The _offal_, in the language of the butcher, constitutes those parts which are not commonly consumed as human food, at least by the well-to-do classes. In calves, oxen, lambs, and sheep, the offal embraces the skin, the feet, and the head, and all the internal organs, excepting the kidneys and their fatty envelope. The offal of the pig is made up of all the internal organs, excepting the kidneys and kidney fat. It is the relative proportion of fat in the carcasses analysed by Lawes and Gilbert that I have stated; but as the nitrogenous matters occur in greatest quantity in the offal, it is necessary that the relative proportions of the constituents of the body, taken as a whole, should be considered. On an average, then, it will be found that a fat fully-grown animal will contain 49 per cent. of water, 33 per cent. of dry fat, 13 per cent. of dry nitrogenous matter--muscles separated from fat, hide, &c.--and 3 per cent. of mineral matter. In a lean animal the average proportions of the various constituents will be 54 per cent. of water, 25-1/2 per cent. dry fat, 17 per cent. of dry nitrogenous substances, and 3-1/2 per cent. of mineral matter. In the following table these proportions are set forth.

SUMMARY OF THE COMPOSITION OF THE TEN ANIMALS--SHOWING THE
PER-CENTAGES OF MINERAL MATTER, DRY NITROGENOUS COMPOUNDS,
FAT, TOTAL DRY SUBSTANCE, AND WATER.

1st. In Fresh Carcass. 2nd. In Fresh Offal (equal Sum of Parts,
excluding Contents of Stomachs and Intestines). 3rd. In Entire
Animal (Fasted Live-weight, including therefore the weight of
Contents of Stomachs and Intestines).

+-----------------------------------------+
| KEY: |
| A.--Mineral matter. |
| B.--Dry nitrogenous compounds. |
| C.--Fat. |
| D.--Dry substance. |
| E.--Water. |
| F.--Contents of viscera. |
| |
----------------------------+-----------------------------------------+
| Per cent. in Carcass. |
DESCRIPTION +--------+--------+-------+-------+-------+
OF ANIMAL. | A. | B. | C. | D. | E. |
----------------------------+--------+--------+-------+-------+-------+
Fat calf | 4.48 | 16.6 | 16.6 | 37.7 | 62.3 |
Half-fat ox | 5.56 | 17.8 | 22.6 | 46.0 | 54.0 |
Fat ox | 4.56 | 15.0 | 34.8 | 54.4 | 45.6 |
Fat lamb | 3.63 | 10.9 | 36.9 | 51.4 | 48.6 |
Store sheep | 4.36 | 14.5 | 23.8 | 42.7 | 57.3 |
Half-fat old sheep | 4.13 | 14.9 | 31.3 | 50.3 | 49.7 |
Fat sheep | 3.45 | 11.5 | 45.4 | 60.3 | 39.7 |
Extra fat sheep | 2.77 | 9.1 | 55.1 | 67.0 | 33.0 |
Store pig | 2.57 | 14.0 | 28.1 | 44.7 | 55.3 |
Fat pig | 1.40 | 10.5 | 49.5 | 61.4 | 38.6 |
----------------------------+--------+--------+-------+-------+-------+
Means of all | 3.69 | 13.5 | 34.4 | 51.6 | 48.4 |
----------------------------+--------+--------+-------+-------+-------+
Means of 8 of the half-fat, | | | | | |
fat, and very fat animals | 3.75 | 13.3 | 36.5 | 53.6 | 46.4 |
----------------------------+--------+--------+-------+-------+-------+
Means of 6 of the fat, | | | | | |
and very fat animals | 3.38 | 12.3 | 39.7 | 55.4 | 44.6 |
----------------------------+--------+--------+-------+-------+-------+

----------------------------+-----------------------------------------+
| Per cent. in Offal. |
Description +--------+--------+-------+-------+-------+
of Animal. | A. | B. | C. | D. | E. |
----------------------------+--------+--------+-------+-------+-------+
Fat calf | 3.41 | 17.1 | 14.6 | 35.1 | 64.9 |
Half-fat ox | 4.05 | 20.6 | 15.7 | 40.4 | 59.6 |
Fat ox | 3.40 | 17.5 | 26.3 | 47.2 | 52.8 |
Fat lamb | 2.45 | 18.9 | 20.1 | 41.5 | 58.5 |
Store sheep | 2.19 | 18.0 | 16.1 | 36.3 | 63.7 |
Half-fat old sheep | 2.72 | 17.7 | 18.5 | 38.9 | 61.1 |
Fat sheep | 2.32 | 16.1 | 26.4 | 44.8 | 55.2 |
Extra fat sheep | 3.64 | 16.8 | 34.5 | 54.9 | 45.1 |
Store pig | 3.07 | 14.0 | 15.0 | 32.1 | 67.9 |
Fat pig | 2.97 | 14.8 | 22.8 | 40.6 | 59.4 |
----------------------------+--------+--------+-------+-------+-------+
Means of all | 3.02 | 17.2 | 21.0 | 41.2 | 58.8 |
----------------------------+--------+--------+-------+-------+-------+
Means of 8 of the half-fat, | | | | | |
fat, and very fat animals | 3.12 | 17.4 | 22.4 | 42.9 | 57.1 |
----------------------------+--------+--------+-------+-------+-------+
Means of 6 of the fat, | | | | | |
and very fat animals | 3.03 | 16.9 | 24.1 | 44.0 | 56.0 |
----------------------------+--------+--------+-------+-------+-------+

----------------------------+-----------------------------------------+
| Per cent. in Entire Animal. |
Description +------+------+------+------+------+------+
of Animal. | A. | B. | C. | D. | F. | E. |
----------------------------+------+------+------+------+------+------+
Fat calf | 3.80 | 15.2 | 14.8 | 33.8 | 3.17 | 63.8 |
Half-fat ox | 4.66 | 16.6 | 19.1 | 40.3 | 8.19 | 51.5 |
Fat ox | 3.92 | 14.5 | 30.1 | 48.5 | 5.98 | 45.5 |
Fat lamb | 2.94 | 12.3 | 28.5 | 43.7 | 8.54 | 47.8 |
Store sheep | 3.16 | 14.8 | 18.7 | 36.7 | 6.00 | 57.3 |
Half-fat old sheep | 3.17 | 14.0 | 23.5 | 40.7 | 9.05 | 50.2 |
Fat sheep | 2.81 | 12.2 | 35.6 | 50.6 | 6.02 | 43.4 |
Extra fat sheep | 2.90 | 10.9 | 45.8 | 59.6 | 5.18 | 35.2 |
Store pig | 2.67 | 13.7 | 23.3 | 39.7 | 5.22 | 55.1 |
Fat pig | 1.65 | 10.9 | 42.2 | 54.7 | 3.97 | 41.3 |
----------------------------+------+------+------+------+------+------+
Means of all | 3.17 | 13.5 | 28.2 | 44.9 | 6.13 | 49.0 |
----------------------------+------+------+------+------+------+------+
Means of 8 of the half-fat, | | | | | | |
fat, and very fat animals | 3.23 | 13.3 | 29.9 | 46.4 | 6.26 | 47.3 |
----------------------------+------+------+------+------+------+------+
Means of 6 of the fat, | | | | | | |
and very fat animals | 3.00 | 12.7 | 32.8 | 48.5 | 5.48 | 46.0 |
----------------------------+------+------+------+------+------+------+