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10. On the other hand, when the nutrient vessels are the most active, the person grows fleshy and corpulent, as in the case of Daniel Lambert, who weighed seven hundred and thirty-nine pounds at the age of forty; or in that of a London butcher, who weighed eight hundred pounds. There are several cases on record, where men weighed eight hundred pounds.

11. (The degree of nutrition, depends much on the quantity and quality of the food. A person who confines himself chiefly to animal diet, and drinks freely of ale and other malt liquors, will usually grow fat; but this does not indicate strength but weakness. It shows that there is not only a weakness of the absorbents, which are not able to take up and remove the fat; but also a muscular debility, and a want of force in the circulation. Motion is impeded; the heart is loaded and oppressed; the breathing is laborious; the blood accumulates in the brain, and the person is every mo. ment exposed to apoplexy.) In all such cases, a sparing diet of vegetables, with proper exercise, will prove an effectual remedy. By sweating, horse-riding, and a low diet, jockeys have not unfrequently reduced themselves 15 or 20 pounds, in a week or ten days.

12. Large accumulations of fat, it is said, sometimes take place, as the sudden effect of the influence of the atmosphere. Thus, in the short space of twenty-four hours, it is stated by writers on natural history, that a mist will occasionally fatten thrushes, robins, &c., to such a degree, than they can hardly get out of the way of the sportsman's gun. This however is not fat, but the appearance is owing to a fulness of the vessels, from a suspension of evaporation.

13. The hump of the camel appears to form a sort of reserve, by which, the Arabs say, he is nourished, during his long journeys. In a period of plenty, the rapid secretion of fat converts it into a pyramid, equalling a fourth of the animal's entire bulk; but a journey through the desert gradually lowers it, so that it becomes scarcely visible. The camel

then gives out, and can travel no further till the store is re plenished by rest and food.*

14. (Tumours, wens, and other morbid growths are the consequence of an error in nutrition.) The nutritious vessels deposite fat where it is not wanted, and occasionally bony mat. ter, where fibrin should be left or something else. In this way only can we account for the bony concretions and scales which are sometimes met with about the heart and blood-vessels; for the chalky deposits about the joints, in cases of gout and rheumatism, and even for horny projec. tions, which have in a few cases been known to sprout out from the head. A few years ago, there were exhibited in London, several individuals called the porcupine family, who were all covered with dark colored horny excrescences; which they shed annually in the autumn or winter. These curious organic peculiarities, resembled the quills of the porcupine, and were two or three inches in length. But these are only exceptions to the usual regularity of nature's operations, and ought, instead of lessening, to increase our admiration at the admirable symmetry and uniformity that prevail, through every department of organized being.

15. (The activity of muscular nutrition, depends much on exercise. The arm of a blacksmith, or a stone-cutter, for instance, is generally large and brawny, because their mus cles are almost in constant use. The same is true of the muscles of the leg, in rope-dancers and tumblers, also in great walkers. Let any one examine the muscles of the Ravel Family, so celebrated for strength and agility in all gymnastic exercises, and he will find them not only unusually developed, but also hard and firm. If a person meet with an accident so that he is unable to walk, although his appetite remains, his muscles dwindle away for want of exercise. If then, a person who leads a sedentary life be corpulent, the excess is not to be considered sound muscle or flesh, but fat, which, I have before stated, is a sign of weakness.

*Burkhardt's travels.

Questions. What is nutrition? What is sought for in constructing a machine? Why the necessity for this? How is it in the animal machine? Is the system constantly undergoing changes How is this shown? What vessels repair the losses of the system? What ani. mals are subject to the most rapid changes of matter? What contains the materials of nutrition? When is nutrition most active ?-when least so? What is the consequence? What does the degree of nutrition depend on? Does fatness indicate strength Why not? What use does the hump of the camel serve? What are tumours and wens owing to? What causes muscular nutrition?

CHAPTER XXIV.

ANIMAL HEAT.

1.(Calorification, is a function of animal bodies, not yet thoroughly understood. We see certain phenomena, but the causes are hidden from our view. It is very doubtful whether we shall ever be able to penetrate the veil which conceals the wonderful operations of vital chemistry; and perhaps it would lead to no useful result if we could; should we ever attain to the knowledge of all the natural laws of life, we shall then be assured that it is only in consequence of their violation that man pays, by suffering, sickness and premature death, the penalty of their transgression.

2. What causes the temperature of the body to be main. tained at an average of ninety-eight degrees, and this, too, under all climates, and at all seasons? In the first place, respiration is much concerned in the production of animal heat. It was once indeed believed, that the chief office of respiration was to cool the blood; and that the heart was the great furnace of the system, where all the heat was pro

duced.

3. (When it was discovered that both in combustion and respiration, carbonic acid was produced, and oxygen ab. sorbed, it was at once surmised, that breathing must be a kind of combustion by which all the heat of the body is generated.) But it was objected to this, that if the heat was all produced in the lungs, why were not the lungs hotter than the other parts of the body, as those parts of a stove in contact with the fuel, are hotter than those at a distance.

4. This objection to Mr. Black's hypothesis, led Mr. Crawford to propose the following solution. Although animal heat is produced in the lungs by the process of respira tion, yet as arterial blood has a greater capacity for caloric

than venous, that is, requires more caloric to preserve it at the same temperature, the heat becomes latent in saturating this increased capacity of arterial blood; and is gradually given off in every part of the body, as the blood assumes the venous character. But unfortunately for this theory, it has been ascertained that there is no difference, and that arterial and venous blood have an equal capacity for heat.

5. But however it may be explained, no one can doubt, that calorification is closely connected with respiration. If the latter is increased by any cause, the heat of the body is also increased. When it is impeded, as in asthma, fainting, breathing deleterious gases, and suffocation the animal heat is sensibly diminished. Those animals whose respiratory apparatus is the most perfect and the best developed, have the highest temperature, as we see in birds, whose bodies are several degrees warmer than the human species.

6. On the contrary, if we look at the cold-blooded animals, we shall find that a large proportion of them live in water, where the supply of oxygen is but scanty, and that their respiration is very imperfect); while in animals that lie torpid during the winter, and are quite cold, respiration is almost if not quite suspended. According to Majendie, respiration produces (four-fifths of the heat in herbivorous animals s(three-fourths in carniverous, and the same in

birds.

7. It is found by experiment, that arterial blood is warmer than venous. The blood is found to acquire one degree of heat in passing through the lungs, and as the whole mass of the blood passes through the lungs twenty times an hour, it follows, that the system receives from respiration twenty degrees of heat in an hour, or two hundred and forty degrees every twelve hours Respiration, then, is one of the chief sources of animal heat.

8. Another theory in relation to animal heat is, that it is produced by, or (depends on, nervous influence. This is

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