| lb. | oz. | |
|---|---|---|
| Frozen seahorse flesh | 4 | 4 |
| Wild seahorse flesh | 4 | 4 |
| Bread and bread dust | 1 | 12 |
| Rich gravy soup | 1 | 4 |
| Water | 10 | 0 |
| Strong grog | 1 tumbler. | |
| Raw spirits | 3 wine glasses. | |
This large quantity of food, which the lad did not consider excessive, was consumed by him within twenty-four hours. According to Captain Cochrane a reindeer suffices but for one repast for three Yakutis, and five of them will devour at a sitting a calf weighing 200 lbs. Mr. Hooper, one of the officers of the Plover, in his narrative of their residence on the shores of Arctic America, states that "one of the ladies who visited them was presented, as a jest, with a small tallow candle, called a purser's dip. It was, notwithstanding, a very pleasant joke to the damsel, who deliberately munched it up with evident relish, and finally drew the wick between her set teeth to clean off any remaining morsels of fat."
The partiality for certain kinds of food, and disgust at other varieties, which particular races of men exhibit, is an instinct which they cannot avoid obeying. Instead of exciting our disgust, as it too frequently does, it should exalt our admiration of the infinite wisdom of the Creator, who by simply adapting man's desire for particular kinds of food to the external conditions under which he is placed, enables him to occupy and "subdue the earth" from the Equator to the Poles.
The food of human beings and of the lower animals who inhabit cold countries is nearly exclusively composed of animal substances. The flesh, fat, and oil of animals occupy less space than do the corresponding elements of vegetables; consequently the nutriment they afford is more concentrated, and a larger quantity can be stowed away without inconvenience in the stomach. The heat-forming constituents of these substances constitute not only the chief part of their bulk, but they are also capable of evolving a greater amount of heat than any other of the respiratory elements. One pound of dry fat will develop as much heat as two and a half pounds of dry starch, and the fattest flesh includes four times as much plastic materials as rice. The diet of people all over the world, unless under circumstances which prevent the gratification of the natural appetite, establishes the intimate relation which subsists between cold and food. The appetite of man is at a minimum at the Equator, and at a maximum within the Arctic circle. The statements as to the voracity of Hottentots and Bosjesmans, recorded in the narratives of travellers, do not in the slightest degree affect the general rule that more is eaten in cold climates than in hot regions. These are mere records of gluttony, and it would not be difficult to find parallel cases in our own country. Gluttony is an abnormal appetite, and the greater part of the food devoured under its unnatural, and generally unhealthy stimulus is not applied to the wants of the body.
The bodies of animals are heated masses of matter, and are subject to the ordinary laws of radiation. Every substance radiates its heat, and receives in return a portion of that emitted from surrounding bodies. If two bodies of unequal temperature be placed near each other, the warmer of the two will radiate a portion of its heat to the colder, and will receive some of the heat of the latter in return; but as the warmer body will emit more heat than it will receive, the result will be, that after a time, the length of which will depend on the nature of the bodies, both will acquire the same temperature. In very warm climates the bodies of animals derive from the sun, and from the heated bodies surrounding them, more heat than they give in return; and were it not for their internal cooling apparatus, which I have described, the heat so absorbed would prove fatal. In every climate, on the contrary, where the temperature is lower than 98°, or "blood heat," the bodies of animals lose more heat by radiation than they receive by the same means. The philosophy of the clothing of men and the sheltering of the lower animals is now evident. It is not only necessary that heat should be developed within the body, but also that its wasteful expenditure should be prevented. The latter is effected by interposing between the warm body and the cold air some substances (such as fur or wool) which do not readily permit the transmission of heat—non-conductors as they are termed. The close down of the eider duck is destined to protect its bosom from the chilling influence of the icy waters of the North Polar Sea, and the quadrupeds of the dreary Arctic Circle are sheltered by thick fur coverings from the piercing blasts of its long winter.
Fat Equivalents.—Whilst it is quite certain that neither nerves nor muscles can be elaborated exclusively out of fat, starch, sugar, or any other non-nitrogenous substance, it is almost equally clear that fat may be formed out of nitrogenous tissue. The quantity of fat, however, which is produced in the animal mechanism, from purely nitrogenous food appears to be relatively very small. No animal is capable of subsisting solely on muscle-forming materials, no matter how abundantly supplied. The food of the Carnivora contains a large proportion of fat, and the nutriment of the Herbivora is largely made up of starch and other fat-formers. Dogs, geese, and other animals fed exclusively upon albumen or white of egg rapidly decreased in weight, and after presenting all the symptoms of starvation, died in three or four weeks.[!--8--][8] The fat of the bodies of the Carnivora is almost entirely formed—and probably with little if any alteration—from the fatty constituents of their food. Herbivorous animals, on the contrary, derive nearly all their fat from starch, sugar, gum, cellulose, and other non-nitrogenous, but not fatty, materials.
Although starch is convertible into fat, it is not to be understood that a pound weight of one of these bodies is equivalent to an equal quantity of the other. During the conversion of starch into fat, the greater number of its constituent atoms is converted into water and carbonic acid gas. The greater number of the more important metamorphoses of organised matter, which take place in the animal organum, is the result of either oxidation or fermentation: in the conversion of starch or sugar into fat or oil, both of these processes, it is stated, take place; a portion of the hydrogen is converted by oxidation into water, and by fermentation carbonic acid gas is formed, which removes both oxygen and carbon. Perhaps in the formation of fat fermentation is alone employed—a portion of the oxygen being removed as water, and another portion as carbonic acid. The chief difference between the ultimate composition of starch and fat is, that the latter contains a much larger proportion of hydrogen and carbon. The knowledge of the exact quantity of starch required for the formation of a given amount of fat is of importance in enabling us to estimate the relative feeding value of both substances. Certain difficulties stand in the way of our acquiring an accurate knowledge on this point. Not only are there several distinct kinds of fat, but the precise formula, or atomic constitution of each, is as yet veiled in doubt. There are three fats which occur in man and the domesticated animals, and in vegetables. These are stearine, margarine, and oleine. The relative proportions of these vary in each animal: thus, in man and in the goose margarine is the most abundant fat, whilst oleine[!--9--][9] exists in the pig in a greater proportion than in man, the sheep, or the ox. The composition of the animal fats does not, however, vary much; and this fact, together with other considerations, have led chemists to assume that two-and-a-half parts of starch are required for the production of one part of the mixed fats of the different animals. Grape sugar and the pectine bodies—substances which form a large proportion of the food of the Herbivora—contain more oxygen and hydrogen than exist in starch, and, consequently, are not capable of forming so large an amount of fat as an equal weight of starch. We may assume, then, that 2·50 parts of starch, 2·75 parts of sugar, or 3 parts of the pectine bodies, are equivalent to 1 part of fat.
SECTION IV.
RELATION BETWEEN THE COMPOSITION OF AN ANIMAL AND THAT OF ITS FOOD.
I have already stated that the results of the admirable investigations of Lawes and Gilbert prove that the non-nitrogenous constituents of the carcasses of oxen, sheep, and pigs exceed in weight their nitrogenous elements. This fact is suggestive of many important questions. What relation is there between the composition of an animal and that of its food? Should an animal whose body contains three times as much fat as lean flesh, be supplied with food containing three times as much fat-formers as flesh-formers? To these questions there is some difficulty in replying. There is a relationship between the composition of the body of an animal and that of its food; but the relationship varies so greatly that it is impossible to determine with any degree of accuracy the quantity of fat-formers which is required to produce a given weight of fat in animals, taken in globo. If, however, we deal with a particular animal placed under certain conditions, it is then possible to ascertain the amount of fat which a given weight of non-plastic food will produce. For the greater part of our knowledge on this point, as on so many others, in the feeding of stock, we are indebted to Lawes and Gilbert. In the case of sheep fed upon fattening food these inquirers found that every 100 lbs. of dry[!--10--][10] non-nitrogenous substances consumed by them produced, on an average, an increase of 10 lbs. in the weight of their fat. In the case of pigs, also, supplied with food, the proportion of non-nitrogenous matters appropriated to the animal's increase was double that so applied in the bodies of the sheep. As the food supplied to these animals contained but a very small proportion of ready-formed fat, it was inferred that four-fifths of the fat of the increase was derived from the sugar, starch, cellulose, and pectine bodies.