RESPIRATION IN ANIMALS.

From careful experiments, it has been found that all animals daily consume a much larger quantity of food than the aggregate of what may have been retained in the system, added to what has been expelled in the fœces and urine, and

what has escaped by perspiration. Boussingault, who combines the characteristics of an ingenious chemist, a vigilant observer, and a practical agriculturist, made an experiment with a "milch-cow and a full-grown horse, which were placed in stalls so contrived that the droppings and the urine could be collected without loss. Before being made the subjects of experiment, the animals were ballasted or fed for a month with the same ration that was furnished to them, during the three days and three nights which they passed in the experimental stalls. During the month, the weight of the animals did not vary sensibly, a circumstance which happily enables us to assume that neither did the weight vary during the seventy-two hours when they were under especial observation.

The cow was foddered with after-math, hay, and potatoes; the horse with the same hay and oats. The quantities of forage were accurately weighed, and their precise degree of moistness and their composition were determined from average samples. The water drunk was measured, its saline and earthy constituents having been previously ascertained. The excrementitious matters passed, were of course collected with the greatest care; the excrements, the urine, and the milk were weighed, and the constitution of the whole estimated from elementary analyses of average specimens of each. The results of the two experiments are given in the table on the next page.

The oxygen and hydrogen that are not accounted for in the sum of the products have not disappeared in the precise proportions requisite to form water; the excess of hydrogen amounts to as many as from 13 to 15 dwts. It is probable that this hydrogen of the food became changed into water by combining during respiration with the oxygen of the air."

FOOD CONSUMED BY THE HORSE IN 24 HOURS.

Forage.	Weight in the wet state	Weight in the dry state		Elementary Matter in the Food.
Forage.	Weight in the wet state	Weight in the dry state		Carbon.		Hydrogen.			Oxygen.			Azote.			Salts and Earths.
	lb.	lb.	oz.	lb.	oz.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.
Hay	20	17	4	7	11	0	10	7	6	8	8	0	3	2	1	6	14
Oats	6	5	2	2	7	0	3	18	1	10	14	0	1	7	0	2	10
Water	43	...		...		...			...			...			0	0	8
Total	69	22	6	10	6	1	2	5	8	7	2	0	4	9	1	9	12

PRODUCTS VOIDED BY THE HORSE IN 24 HOURS.

Products.	Weight in the wet state			Weight in the dry state			Elementary Matter in the Food.
Products.	Weight in the wet state			Weight in the dry state			Carbon.			Hydrogen.			Oxygen.			Azote.			Salts and Earths.
	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.
Urine	3	6	15	9	9	14	0	3	10	0	0	7	0	1	2	0	1	4	0	3	10
Excrements	38	2	2	9	5	6	3	7	17	0	5	15	3	6	14	0	2	10	1	6	10
Total	71	8	17	10	3	0	3	11	7	0	6	2	3	7	16	0	3	14	1	10	0
Total matter of the food	69	0	0	22	6	0	10	6	0	1	2	5	8	7	2	0	4	9	1	9	12
Difference	27	3	3	12	3	0	6	6	13	0	8	3	4	11	6	0	0	15	0	0	12

WATER CONSUMED BY THE HORSE IN 24 HOURS.			WATER VOIDED BY THE HORSE IN 24 HOURS.
	lbs.	oz.		lbs.	oz.
With the hay	2	3	With the urine	2	6
With the oats	0	14	With the excrements	23	8
Taken as drink	35	3
Total consumed	38	4	Total voided	25	14
			Water consumed	38	4
Water exhaled by pulmonary and cutaneous transpiration				12	6

FOOD CONSUMED BY THE COW IN 24 HOURS.

Fodder.	Weight in the wet state			Weight in the dry state			Elementary Matter in the Food.
Fodder.	Weight in the wet state			Weight in the dry state			Carbon.			Hydrogen.			Oxygen.			Azote.			Salts and Earths.
	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.
Potatoes	40	2	5	11	2	1	4	11	2	0	7	15	4	10	17	0	1	12	0	6	13
After-math hay	20	1	2	16	11	0	7	11	11	0	11	7	5	10	17	0	4	17	1	8	6
Water	160	0	0	...			...			...			...			...			0	1	12
Total	220	3	7	28	1	1	12	10	13	1	7	2	10	9	14	0	6	9	2	4	11

PRODUCTS VOIDED BY THE COW IN 24 HOURS.

Products.	Weight in the wet state			Weight in the dry state			Elementary Matter in the Food.
Products.	Weight in the wet state			Weight in the dry state			Carbon.			Hydrogen.			Oxygen.			Azote.			Salts and Earths.
	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.	lb.	oz.	dwt.
Excrements	76	1	9	10	8	12	4	7	0	0	6	13	4	0	9	0	2	19	1	3	8
Urine	21	11	12	2	6	17	0	8	7	0	0	16	0	8	3	0	1	3	1	0	6
Milk	22	10	10	3	1	0	1	8	3	0	3	3	0	10	6	0	1	9	0	1	16
Total	120	11	11	16	4	9	6	11	10	0	10	12	5	6	18	9	5	11	2	5	10
" matter of food	220	3	7	28	1	1	12	10	13	1	7	2	10	9	14	0	6	9	2	4	11
Difference	99	3	16	11	8	12	5	11	3	0	8	10	5	2	16	0	0	18	0	0	19

WATER CONSUMED BY THE COW IN 24 HOURS.			WATER VOIDED BY THE COW IN 24 HOURS.
	lbs.	oz.		lbs.	oz.
With the potatoes	23	12	With the excrements	53	10
With the hay	2	9	With the urine	15	14
Taken as drink	132	0	With the milk	16	3
Total consumed	158	5	Total voided	85	11
			Water consumed	158	5
Water passed off by pulmonary and cutaneous transpiration				79	2

We here perceive a large loss of water, carbon, hydrogen, &c. Nearly all this loss of carbon and hydrogen escaped by respiration, while most of the water, oxygen, nitrogen, and salts, passed off in perspiration. In further illustration of the subject of respiration, Liebig says, "from the accurate determination of the quantity of carbon daily taken into the system in the food, as well as of that proportion of it which passes out of the body in the fœces and urine, unburned, that is, in some form uncombined with oxygen, it appears that an adult taking moderate exercise, consumes 13.9 oz. of carbon daily." The foregoing are facts in the animal economy, capable of vast practical bearing in the management of our domestic animals. But before following out these principles to their application, let us briefly examine

The Effects of Respiration.

We have seen from the experiment of Boussingault, that there is a loss of 6 lbs. 6 oz. of carbon, and 8 oz. 3 dwt. of hydrogen in the food of the horse, and something less in that of the cow, every 24 hours, which has not been left in the system, nor has it escaped by the evacuations. What has become of so large an amount of solid matter? It has escaped through the lungs and been converted into air. The carbon and hydrogen of the food have undergone those various transformations which are peculiar to the animal economy, digestion, assimilation, &c., which it is not necessary, nor will our limits permit us here to explain; and they appear at last in the veinous blood, which in the course of its circulation is brought into the cells of the lungs. The air inhaled is sent through every part of their innumerable meshes, and is there separated from the blood, only by the delicate tissues or membranes which enclose it. A portion of the carbon and hydrogen escapes from the blood into the air-cells, and at the instant of their contact with the air, they affect a chemical union with its oxygen, forming carbonic acid and the vapor of water, which is then expired, and a fresh supply of oxygen is inhaled. This operation is again repeated, through every successive moment of animal existence.

Besides other purposes which it is probably designed to subserve, but which have hitherto eluded the keenest research of chemical physiology, one obvious result of respiration is, the elevation of the temperature of the animal system. By the ever-operating laws of nature, this chemical union of two

bodies in the formation of a third, disengages latent heat, which taking place in contact with the blood, is by it diffused throughout the whole frame. The effect is precisely analogous to the combustion of fuel, oils, &c., in the open air.

Perspiration

Is the counteracting agent which modifies this result, and prevents the injurious effects, which, under exposure to great external heat, would ensure certain destruction. And this too, it will have been seen, is provided at the expense of the animal food. When from excessive heat, caused by violent exercise or otherwise, by which respiration is accelerated and the animal temperature becomes elevated, the papillæ of the skin pour the limpid fluid through their innumerable ducts, which in its conversion into vapor, seize upon the animal heat and remove it from the system, producing that delicious coolness so grateful to the laboring man and beast in a sultry summer's day. These two opposing principles, like the antagonistic operations of the regulator in mechanics, keep up a perfect balance in the vital machine, and enable that entire division of the animal creation, distinguished as warm-blooded, including man and the brute, all the feathered tribes, the whale, the seal, the walrus, &c., to maintain an equilibrium of temperature, whether under the equator or the poles; on the peaks of Chimborazo, the burning sands of Zahara, or plunged in the depths of the Arctic Ocean.

The connection between the size of the lungs, and the aptitude of animals to fatten, will be more apparent from the fact, that the carbon and hydrogen which are abstracted, constitute two of the only three elements of fat. The larger size, the fuller play, and the greater activity of the lungs, by exhausting more of the materials of fat, must necessarily diminish its formation in the animal system; unless it can be shown, which has never yet been done, that the removal of a portion of the fat-forming principles accelerates the assimilation of the remainder.

The Food which supplies Respiration.

This, in the herbivorous animals, after they are deprived of the milk, which furnishes it in abundance, is the starch, gum, sugar, vegetable fats, and oils that exist in the vegetables, grain, and roots which they consume; and in certain cases

where there is a deficiency of other food, it is sparingly furnished in woody and cellular fibre. All these substances constitute the principal part of dry vegetable food, and are made up of three elements, which in starch, gum, cane-sugar, and cellular fibre, exist in precisely the same proportions, viz: 44 per cent. of carbon, 6.2 of hydrogen, and 40.8 of oxygen.

Grape sugar, woody fibre, and vegetable and animal fats and oils are made up of the same elements, but in different proportions, the last containing much more carbon and hydrogen than those above specified. In the fattening animals, it is supposed the vegetable fats and oils are immediately transferred to the fat cells, undergoing only such slight modification as perfectly adapts them to the animal economy, while respiration is supplied by the other enumerated vegetable matters. If these last are taken into the stomach beyond the necessary demand for its object, they too are converted by the animal functions into fat, and are stored up in the system for future use. But if the supply of the latter is insufficient for respiration, it first appropriates the vegetable fat contained in the food; if this is deficient, it draws on the accumulated stores of animal fat already secreted in the system, and when these too are exhausted, it seizes upon what is contained in the tissues and muscle. When the animal commences drawing upon its own resources for the support of its vital functions, deterioration begins; and if long continued, great emaciation succeeds, which is soon followed by starvation and death.

The carnivorous animals are furnished with their respiratory excretions, from the animal fat and fibre which exist in their food, and which the herbivoræ had previously abstracted from the vegetable creation.

Circumstances which augment Respiration.

These are, exercise, cold, and an abundant supply of food. Exercise, besides exhausting the materials of fat, produces a waste of fibre and tissue, the muscular and nitrogenized parts of the animal system; and it is obvious from the foregoing principles, that cold requires a corresponding demand for carbon and hydrogen to keep up the vital warmth. The consumption of food to the fullest extent required for invigorating the frame, creates a desire for activity, and it insensibly induces full respiration. The well-fed, active man, unconsciously draws a full, strong breath; while the abstemious and the feeble, unwittingly use it daintily, as if it were a choice com

modity not to be lavishly expended. If the first be observed when sleep has effectually arrested volition, the expanded chest will be seen, heaving with the long-drawn, sonorous breath; while that of the latter will exhibit the gentle repose of the infant on its mother's breast.

The difference between the food of the inhabitants of the polar and equatorial regions, is strikingly illustrative of the demands both for breathing and perspiration. The latter are almost destitute of clothing, and subsist on their light, juicy, tropical fruits, which contain scarcely 12 per cent. of carbon, yet furnish all the elements for abundant perspiration; while the former are imbedded in furs, and devour gallons of train oil or its equivalent of fat, which contains nearly 80 per cent. of carbon, that is burnt up in respiration to maintain a necessary warmth.

The bear retires to his den in the beginning of winter, loaded with fat, which he has accumulated from the rich, oily mast abounding in the woods in autumn. There he lies for months, snugly coiled and perfectly dormant; the thickness of his shaggy coat, his dry bed of leaves, and well-protected den, effectually guarding him from cold, which in addition to his want of exercise, draw slightly upon respiration to keep up the vital heat. When the stores of carbon and hydrogen contained in the fat are expended, his hunger and cold compel him to leave his winter-quarters, again to wander in pursuit of food.

Many of the swallow tribes, in like manner, hybernate in large hollow trees, and for months eke out a torpid, scarcely perceptible existence, independent of food. Activity and full respiration, on the return of spring, demand a support, which is furnished in the myriads of flies they daily consume. The toad and frog have repeatedly been found in a torpid state, imbedded in limestones, sandstones, and the breccias, where they were probably imprisoned for thousands of years without a morsel of food; yet when exposed to the warmth of the vital air and the stimulus of its oxygen, they have manifested all the activity of their species. This they are enabled to sustain only by an enormous consumption of insects.

Dr. Playfair states, that in an experiment made by Lord Ducie, 100 sheep were placed in a shed, and ate 20 pounds of Swedes turnips each per day; another 100 were placed in the open air, and ate 25 pounds per day; yet the former, which had one-fifth less food, weighed, after a few weeks, three pounds more per head than the latter. He then fed five sheep

in the open air, between the 21st November and 1st December. They consumed 90 pounds of food per day, the temperature being at 44°, and at the end of this time, they weighed two pounds less than when first exposed. Five sheep were then placed under a shed, and allowed to run about in a temperature of 49°. At first they consumed 82 pounds per day; then 70 pounds, and at the end of the time they had gained 23 pounds. Again, five sheep were placed under a shed as before, and not allowed to take any exercise. They ate at first, 64 pounds of food per day, then 58 pounds, and increased in weight 30 pounds. Lastly, five sheep were kept quiet and covered, and in the dark. They ate 35 pounds per day, and increased eight pounds.

Mr. Childers states, that 80 Leicester sheep in the open field, consumed 50 baskets of cut turnips per day, besides oil-cake. On putting them in a shed, they were immediately able to consume only 30 baskets, and soon after but 25, being only half the quantity required before, and yet they fattened as rapidly as when eating the largest quantity. The minimum of food, then, required for the support of animals, is attained when closely confined in a warm, dark shelter; and the maximum, when running at large, exposed to all weathers.