" THE FOOD OF ANIMALS AND OF MAN.

IN this little work we have laid before us a very explicit and intelligible account of a long series of experiments made at the instance of the Go- vernment, together with some general principles of great practical im- portance deduced from them by the author. The inquiry was originally instituted with a view to determine the relative efficacy of barley and malt as food for cattle; but it was extended so as to embrace certain physiological problems of extreme value with regard to the physical management of animals and man. The subjects of the experiments were two milch cows, selected with great care from a large herd, and stall-fed on "various kinds of fodder, viz, grass, chopped hay, barley whole and crushed and scalded, malt, barley and molasses, barley and linseed, and bean-meal. The animals themselves, their food, milk, butter, &c., and their ejects, were weighed every day ; and thus the useful effect of each kind of diet was ascertained. Some of the most notable facts thus empirically established were as follows.

Great advantage is derived from the mechanical division of the food of cattle ; for it is a saving of so much labour to the digestive organs. When barley was given whole to the two cows, much of it remained unaltered by the process of digestion. As to the amount of grain best calculated to afford the largest supply of milk, this remarkable principle appears to have been fully established—that the daily allowance of barley or malt (along with bulky food) should not exceed nine pounds; otherwise, the milk diminishes instead of increasing in quantity. The author ex- plains this physiologically. In all animals, especially ruminants, which possess great capacity of stomach, an excess of concentrated food, by failing to effect adequately what bulky food accomplishes—to excite the coats of the stomach to secrete their digestive fluid—will prove injurious. The use of malt as fodder is to be condemned both absolutely and rela- tively: it is inferior to barley, as it gives less milk and butter, and the animal fed upon it falls off in weight. For feeding it is a much more expensive substance, irrespectively of the duty, than barley, inasmuch as it is in reality barley deprived of a certain portion of its nutritive matter and salts. It may be used with advantage to give a relish to a mash by its sweetening properties. According to Payen, a handful of malt would be sufficient to saccharize several pounds of barley in the steep ; that is, to convert the starch contained in them into sugar. The quantity of butter obtained in the experiments was not proportioned to the oleaginous nature of the food : linseed gave less than bean-meal, although containing twice as much oil, probably because beans are better suited to the general support of the animal economy. On reviewing the whole body of the experiments, it is found to be a pretty uniform result, that a change of food produces an increase in the quantity of milk, and that after the same diet has been continued for some days the milk begins to diminish in amount. This is accordant with the well-known superior grazing qualities of old natural pastures, made up of a variety of grasses and other plants, as compared with those pastures which consist of only one grass. The experiments evince beyond all doubt, that cattle, especially milch cows, in a state of confinement would be benefited by a very fre-

quent and entire change in their food ; and Dr. Thomson would be dis- posed to recommend a daily modification of the dietary of such animals. Extending these views to the food of man, the author says-

" The results now obtained amply sustain the idea supported by me some time ago in reference to the dietary of human beings shut up in poor-houses and places of confinement. It was then argued that, order to retain the human consti- tution in a healthy condition, variety of food should be properly attended to' and different species of diet were suggested as well calculated to supply a series of dishes to the poor. In the Asylum for the Houseless, and in the House of Refuge at Glasgow, the recommendations were followed out; and, according to the report of the treasurer, Mr. Liddell, the dinner-meals being varied two or three times every week, 'the change in the dietary routine is much relished by the inmates, and may have had some effect in the greater degree of health which has been evi- dent among them of late.' • "A cow, if fed for two days on an insufficient quantity of food, as indicated by loss of weight and diminution of milk, will. require at least double that time to reach the condition from which it had deteriorated; and the reason of this is ob- vious, because the partial starvation has caused it to lose a portion of the enb- stance of its body, which requires a longer time to reestablish than to pull down. This rule is applicable to the dietary of men as well as the inferior animals. An increase of labour should always be accompanied with an increase of food, both at sea and in prison; a short walk to one confined in a solitary cell calls for some augmentation of food. A slight increase of temperature, or the irritating influ- ence of insects, will effectually diminish the milk of a cow, and indicates the pro- priety of increasing the amount of fodder."

To ordinary readers it may at first sight appear impossible to reason very closely from the food of cows to that of men ; for what analogy is there between a rump-steak and a bundle of dry hay ? The objection is specious, but hollow : there is not only analogy in the case, but actual identity, disguised only by difference of combination aud form. All flesh is literally grass,—both our own living flesh and that which we eat. Our bodies are built up of the elements of those substances we con- sume for food, and are continually resolved into them again both in life and after death. The same thing is true likewise of the lower ani., male. Moreover, the blood contains all the ingredients that go to form the body ; and as the blood of cows is identical in composition with that of the human species, it is obvious that the diet of the one class of ani- mals must possess a similar composition to that of the other. If, there- fore, we discuss the subject not as cooks, but as physiologists and che- mists, we shall detect the principle of unity that lies hid under all its apparent diversity, and shall find that the laws of dietetics resolve them- selves finally into the same general expressions both for man and beast.

The food of animals consists in the last analysis of hydrogen, nitrogen, oxygen, and carbon, variously combined, and of saline matters. Its use is twofold ; a part goes to supply the incessant waste of the body, by depositing fresh particles of flesh, bone, membrane, nerve, &c., in the place of those that are taken up into the circulation and east out of the system. This is the nutritive portion of the food : the other, of which carbon is the main ingredient, is what Liebig calls the respiratory, and Dr. Thomson the ealoriftant or heat-prodtwing portion. It is, in fact, and without a metaphor, the fuel by which animal heat is sustained. The oxygen of the air combining with the carbon of the blood in the ca- pillary vessels of the lungs, stomach, and skin, converts it into carbonic acid, condensation takes place, and heat is given out. The process is the same in kind as the burning of wood, coal, or other carbonaceous matter, in the open air: the difference is only in degree. The following table gives approximately the proportion of nutritive to oalorifiant matter in several kinds of food.

Relation of Nutritive to Caloriflant.

"Milk. Food for a growing animal Ito 2

Beans 1 — 211 Oat-meal 1 — 5 Semolina, Barley 1 — 7 English Wheat-flour. Food for an animal at rest

1— fir

Potatoes 1 — 9 Rice 1 — 10 Turnips 1 — 11 Arrow-root, Tapioca, Sago 1 — 26 Starch 1-40

"From this table we are led to infer that the food destined for the animal in a state of exercise should range between milk and wheat-flour, varying in its degree of dilution with calorifiant matter according to the nature and extent of the de- mands upon the system. The animal system is thus viewed as in an analogous condition to a field from which different crops extract different amounts of matter from the soil, which must be ascertained by experiment. An animal at rest con- sumes more calorifiant food in relation to the nutritive constituents than an ani- mal in full exercise. The food, therefore, employed by a person of sedentary habits should contain more calorifiant and less nutritive matter than one whose occupations cause him to take more exercise. It is to be desired that some light should be thrown on this subject by careful experiments. The food of animals and the manure of plants we thus see afford somewhat of a parallelism. Milk may therefore be used with a certain amount of farinaceous matter, such as the class of flours and meals, with probable advantage; but the dilution should not exceed the prescribed limits. It is thus that we may explain the fact of beans, oats, oat-meal, and barley-meal, being used so extensively in the feeding of horses. These articles of food, however, do not suffice alone: calorifiant matter in the form of hay should also be administered. From this table, likewise, we infer that as nature has provided milk for the support of the infant mammalia, the consti- tution of their food should always be formed after this type. Hence we learn that milk, in some form or other, is the true food of children; and that the use of arrow-root, or say of the members of the starch class, where the relation of the nutritive to calorifiant matter is as 1 to 26, instead of being as 1 to 2, by an animal placed in the circumstances of a human infant, is opposed to the princi- ples unfolded by the preceding table. In making this statement, I find that there are certain misapprehensions into which medical men are apt to be led at the first view of the subject. To render it clearer, let us recall to mind what the arrow-root class of diet consists of. Arrow-root and tapioca are prepared by washing the roots of certain plants until all the matter soluble in water is re- moved. Now, as albumen is soluble in water, this form of nutritive matter must in a great measure be washed away : under this aspect we might view the origi- nal root, before it was subjected to the washing process, to approximate in compo- sition to that of flour. lithe latter substance were washed by repeated additions of water the nitrogenous or nutritive ingredients would be separated from the starchy or calorifiant elements, being partly soluble in water, and partly mechanically removed. Arrow-root, therefore, may be considered as flour deprived as much as possible of its nutritive matter. When we ad. minister arrow-root to a child, it is equivalent to washing all the nu- tritive matter out of bread, flour, or oat-meal, and supplying it with the starch; or it is the same thing approximately as if we gave it starch; and this is in fact what is done, when children are fed upon what is sold in the shops under the title of farinaceous food, empirical preparations of which no one can understand the composition without analysis. Of the bad effects produced in children by the use of these most exceptionable mixtures, I have had ample opportunities of forming an opinion; and I am inclined to infer that many of the irregularities of the bowels, the production of wind, &c, in children, are often attributable to the use of such unnatural species of food. How often are the ears of parents and nurses distressed with the agonizing cries of the helpless child, and how often are these symptoms of suffering treated as the effects of ill-humour, or of causeless peevish- ness; when, on the contrary, they have been produced by the improper diet in many cases with which the child has been supplied. It should be remembered that all starchy food deprived of nutritive matter is of artificial production, and

i scarcely, if ever, exists n nature in an isolated form. The administration of the arrow-root class is therefore cnly admissible when a sufficient amount of nutritive matter has been previously introduced into the digestive organs, or when it is in- advisable to supply nutrition to the system; as in cases of inflammatory action. In such instances, the animal heat must be kept up; and for this purpose calori- Sant food alone is necessary. This treatment is equivalent to removing blood from the system; since the waste of the fibrinous tissues goes on, while an ade- quate reparation is not sustained by the introduction of nutritive food."

Following out these principles, Dr. Thomson recommends the practice of mixing different kinds of flour together, so that the one may com- pensate for the defects of the other ; and he gives various prescriptions for making wholesome palatable bread in this way. Ile deservedly con- demns the employment of yeast in making bread : its only use is to render the dough light and spongy by inflating it with the carbonic acid gas which escapes from the fermented mass; but the gas could be obtained quite as well by mixing with the dough muriatic acid and carbonate of soda, the ingredients of common table-salt. When yeast is used, the fer- mentation destroys one of the most important elements of the flour. "The result of my experiments upon the bread produced by the action of hy- drochloric acid upon carbonate of soda, has been, that in a sack of flour there was a difference in favour of the unfermented bread to the amount of 30 pounds 13 ounces; or, in round numbers, a sack of flour would produce 107 loaves of unfer- mented bread, and only 100 loaves of fermented bread of the same weight. Hence it appears, that in the sack of flour by the common process of baking, 7 loaves, or Si per cent of the flour, are driven into the air and lost. * • *

"A good method of making unfermented bread is to take of flour 4 pounds. Sesquicarbonate of soda, (supercarbonate of the shops,) 320 grains. Hydrochloric acid, (spirit of salt or muristic acid of the shops,) 6.11 fluid drachms. Common salt, 300 grains. Water, 35 ounces by measure. The soda is first mixed with the flour very intimately. The salt is dissolved in the water, and added to the acid. The whole being then rapidly mixed as in common baking. The bread may either be baked in tins or firmed like cottage-loaves, and should be kept from one to two hours in the oven. Should the bread prove yellow, it is a proof that the soda has been in excess, and indicates the propriety of adding a small additional portion of acid; the acid varying somewhat in strength. The same process may be employed in raising the other mixture previously recommended."

Here is a hint worth attending to.

"Mode of preserving butter fresh.—The cause of the tainting of fresh butter depends upon the presence of the small quantity of curd and water as exhibited by the preceding analysis. To render butter capable of being kept for any length of time in a fiuh condition, that is, as a pure solid oil, all that is necessary is to bon it in a•pan till the water is removed, which is marked by the cessation of vio- lent ebullition. By allowing the liquid oil to stand for a little the curd subsides, and the oil may then be poured off, or it may be strained through calico or mus • lin, into a bottle, and corked up. When it is to be used it may be gently heated and poured out of the bottle, or cut out by means of a knife or cheese-gouge. This is the usual method of preserving butter in India, (ghee,) and also on the Continent; and it is rather remarkable that it is not in general use in this coun- try. Bottled butter will thus keep for any length of time; and is the best form of this substance to use for sauces.'

The author has forgot to mention that the vessel containing the butter should not be put naked on the fire, but immersed in another containing water. If this precaution be not observed the butter will be overheated and spoiled.