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Lastly, the possession of sensibility and locomotility leads to other characteristics of animated beings. These functions are incapable of constant, unremitting exertion. Sleep, therefore, becomes necessary. The animal is also capable of expression, or of language, in a degree proportionate to the extent of his sensibility, and of his power over the beings that surround him.

But these differences in function are not so discriminate as they may appear at first. There are many animals, that are as irresistibly attached to the soil as the vegetables themselves. Like the latter, they must, of necessity, be compelled to absorb their food in the state in which it is presented to them. Sensibility and locomotility appear, in the zoophyte, to be no more necessary than in the vegetable. No nervous, no muscular system is required; and, accordingly, none can be traced in them; whilst many of those spontaneous motions of the vegetable, to which allusion has been made, have been considered by some to indicate the first rudiments of sensibility and locomotility; and Linnæus1 has regarded the closure of the flowers towards night as the sleep, and the movements of vegetables, for the approximation of the sexual organs, as the marriage, of plants.

II. GENERAL PHYSIOLOGY OF MAN.

The observations made on the differences between animals and vegetables have anticipated many topics, that would require consideration under this head. These general properties, which man possesses along with other animals, have been referred to in a cursory manner. They will now demand a more special investigation.

1. MATERIAL COMPOSITION OF MAN.

The detailed study of human organization is the province of the anatomist, of its intimate composition, that of the chemist. In explaining the functions executed by the various organs, the physiologist will frequently have occasion to trench upon both.

The bones, in the aggregate, form the skeleton. The base of the skeleton is a series of vertebræ, with the skull as a capital,-itself regarded as a vertebra. This base is situate on the median line through the whole trunk, and contains a cavity, in which are lodged the brain and spinal marrow. On each side of this, other bones, which by some have been called appendices, are arranged in pairs. Upon the skeleton are placed muscles, for moving the different parts of the body; and for changing its situation with regard to the soil. The body is divided into trunk and limbs. The trunk, which is the principal portion, is composed of three splanchnic cavities, the abdomen, thorax, and head, situate one above the other. They contain the most important organs of the body,—those that effect the functions of sensibility, digestion, respiration, circulation, &c. The head comprises the face, in which are the organs of four of the senses-sight, hearing, smell, and taste,— and the cranium, which lodges the brain-the organ of the mental manifestations, and the most elevated part of the nervous system. The

'Amœnit. Academ., tom. iv.

thorax or chest contains the lungs-organs of respiration-and the heart, the central organ of the circulation. The abdomen contains the principal organs of digestion, and (if we include in it the pelvis), those of the urinary secretion and of generation. Of the limbs, the upper, suspended on each side of the thorax, are instruments of prehension; and are terminated by the hand, the great organ of touch. The lower are beneath the trunk; and are agents for supporting the body, and for locomotion. Vessels, emanating from the heart, are distributed to every part, conveying to them the blood necessary for their life and nutrition: these are the arteries. Other vessels communicate with them, and convey the blood back to the heart-the veins; whilst a third set arise in the tissues, and convey into the circulation, by a particular channel, a fluid called lymph-whence they derive the name lymphatics. Nerves, communicating with the great central masses of the nervous system, are distributed to every part; and lastly, a membrane or layer, possessed of acute sensibility-the skin-serves as an outer envelope to the whole body.

It was before observed, that two kinds of elements enter into the composition of the body-the chemical or inorganic; and the organic, which are compound, and formed only under the force of life.

The chief CHEMICAL or INORGANIC ELEMENTS, met with, are-oxygen, hydrogen, carbon, nitrogen, phosphorus, calcium; and, in smaller quantity, sulphur, iron, manganese, calcium, silicium, aluminium, chlorine; also, sodium, magnesium, &c. &c.

1. Oxygen. This is widely distributed in the solids and fluids; and a constant supply of it from the atmosphere is indispensable to animal life. It is almost always found combined with other bodies; often in the form of carbonic acid,-that is, united with carbon. In a separate state it is met with in the air-bag of fishes, in which it is found varying in quantity, according to the species, and the depth at which the fish has been caught.

2. Hydrogen. This gas occurs universally in the animal kingdom. It is a constituent of all the fluids, and of many of the solids; and is generally in a state of combination with carbon. In the human intestines it has been found pure, as well as combined with carbon and sulphur.

3. Carbon. This substance is met with under various forms, in both fluids and solids. It is most frequently found under that of carbonic acid. Carbonic acid has been detected in an uncombined state in urine by Prout; and in the blood by Vogel. It exists in the intestines of animals; but is chiefly met with in animal bodies, in combination with the alkalies or earths; and is emitted by all animals in the act of respiration.

4. Nitrogen. This gas is likewise widely distributed as a component of animal substances, and especially of the tissues. It occurs in an uncombined state, in the swimming-bladder of certain fishes.

5. Phosphorus is an essential constituent of neurine; and is found united with oxygen, in the state of phosphoric acid, in many of the

'Annals of Philosophy, vii. 56.

solids and fluids. It is this acid that is combined with the earthy matter of bones; and with potassa, soda, ammonia, and magnesia, in other parts. It is supposed to give rise to the luminousness of certain animals-as of the firefly, Pyrosoma Atlanticum, &c.-but nothing precise is known on this subject.

6. Calcium.-This metal is found in the animal economy only in the state of oxide-lime; and it is generally united with phosphoric or carbonic acid. It is the earth, of which the hard parts of animals are constituted.

7. Sulphur is not met with extensively in animal solids or fluids; nor is it often found free, but usually in combination with oxygen united to soda, potassa, or lime. It seems to be an invariable concomitant of albumen; and is found in the intestines, in the form of sulphuretted hydrogen; and as an emanation from fetid ulcers.

8. Iron. This metal has been detected in the colouring matter of the blood; in bile, and in milk. In the first of these fluids it was, for a long time, considered to be in the state of phosphate or sub-phosphate. Berzelius' showed, that this was not the case; that the ashes of the colouring matter always yielded oxide of iron in the proportion of 1-200th of the original mass. That distinguished chemist was, however, unable to detect the condition in which the metal exists in the blood; and could not discover its presence by any of the liquid tests. Subsequently, Engelhart showed, that the fibrin and albumen of the blood, when carefully separated from colouring particles, do not contain a trace of iron; whilst he could procure it from the red corpuscles by incineration. He also succeeded in proving its existence in the red corpuscles by liquid tests; and his experiments were repeated, with the same results, by Rose of Berlin. In milk, iron seems to be in the state of phosphate.

9. Manganesium has been found in the state of oxide, along with iron, in the ashes of the hair; in bones, and blood, and also in gallstones, and in the blood.

10. Copper and lead.-It was conceived by M. Devergie, that copper and lead may exist naturally in the tissues;3 but MM. Flandin and Danger, and a commission of the Académie Royale de Médecine of Paris, were unable to confirm the existence of copper; and the results of the investigations of Professor F. de Cattanei di Momo, of Pavia, seem to prove the non-existence of lead also. M. Barse, however, in a paper read before the Royal Academy of Sciences of Paris, in August, 1843, states, that he found both metals in the bodies of two persons, to whom they could not have been given for poisons. The researches of Signor Cattanei di Momo appeared to prove that these metals do not exist in the bodies of new-born children or infants; and M. J. Rossignon has offered a solution as to the probable source of the copper, as he found it not only in the blood and muscles of the dog, but in

'Medico Chirurgical Transact., vol. iii.

"Turner's Chemistry, fifth ed., p. 963. London, 1834.

3 Bullet. de l'Académ. Royale de Médecine, 19 Févr., 1839.

4 Annali Universali di Medicina, Aprile, 1840; cited in British and Foreign Medical Re view, Jan., 1841, p. 226.

many articles of vegetable and animal food; in gelatin from bones, for example, in sorrel, chocolate, bread, coffee, succory, madder, and sugar. The ashes obtained from starch sugar yielded 4 per cent. of copper; those of gelatin, 0.03 per cent.; and those of bread, 0·005 to 0.008 per cent. It is now generally considered to be present in the human liver, and M. E. Millon3 asserts, that human blood invariably contains lead, copper, silica, and manganese.

11. Silicium.-Silica is found in the hair, bones, blood, urine, and in urinary calculi.

12. Chlorine. In combination with hydrogen, and forming chlorohydric acid, chlorine is met with in most of the animal fluids. It is generally united with soda. Free chlorohydric acid has also been found by Dr. Prout in the stomach of the rabbit, hare, horse, calf, and dog; and he has discovered the same acid in the sour matter ejected from the stomachs of those labouring under indigestion. Mr. Children, and Messrs. Tiedemann and Gmelin,' made similar observations; and Professor Emmet and the author found it in considerable quantity in the healthy gastric secretions of man.

13. Fluorine. This simple substance has been found combined with calcium-fluoride of calcium-in the enamel of the teeth, bones, and

urine.

14. Sodium.-Oxide of sodium, soda, forms part of all the fluids. It has never been discovered in a free state; but is united (without an acid), to albumen. Most frequently, it is combined with chlorine, and phosphoric acid; less frequently, with lactic, carbonic, and sulphuric acids. Chloride of sodium is contained in most of the animal secretions; and from its decomposition may result the chlorohydric acid of the gastric juice, and a part the soda of the bile and other fluids.

15. Potassium.-The oxide, potassa, is found in many animal fluids, but always united with acids-sulphuric, chlorohydric, phosphoric, &c. It is much more common in the vegetable kingdom; and hence one of its names-vegetable alkali.

16. Magnesium.—The oxide, magnesia, exists sparingly in bones, and in some other parts; but always in combination with phosphoric acid, and appears to be always associated with calcium.

17. Aluminium.—Alumina is said by Morichini to exist in the enamel of the teeth. Fourcroy and Vauquelin found it in the bones; and John, in white hairs. According to Schlossberger, it is in the flesh of

fishes."

18. Titanium.-Dr. Rees affirms, that he detected it in salts obtained from the supra-renal capsules.

Lond. Med. Gaz., Dec. 1, 1843, from Gazette Médicale de Paris, and Mr. Paget, Rep. on Anatomy and Physiology, 1843-4, in Brit. and For. Med. Rev., Jan., 1845, p. 249.

2 Kirkes and Paget, Manual of Physiology, Amer. edit., p. 29, Philad., 1849.

3 Comptes Rendus, Paris, 1848.

4 Philosoph. Transact. for 1824, p. 45.

5 Recherches Expérimentales, &c., sur la Digestion, trad. par A. G. L. Jourdan. Art. 4, p. 94, Paris, 1827.

6 See under the head of "Digestion," and the author's Human Health, p. 191, Philadelphia,

1844.

7 Henle, Allgemeine Anatomie, s. 4. Leipz., 1841, or Jourdan's translation, i. 2, Paris,

19. Arsenic. It was asserted by M. Orfila, that arsenic exists naturally in the human body; and that it is a normal constituent of human bones. Subsequent experiments, however, performed by M. Orfila himself, have shown that there was fallacy in his first observations.1

ORGANIC ELEMENTS, proximate principles or compounds of organization, are combinations of two or more of the elementary substances, in definite proportions. Formerly, four only were admitted-gelatin, fibrin, albumen, and oil. Of late, however, organic chemistry has pointed out others, which are divided into two classes,-first, those that contain nitrogen, as albumen, gelatin, fibrin, osmazome, mucus, casein, urea, uric acid, red colouring principle of the blood, yellow colouring principle of the bile, &c.; and secondly, those that do not contain azote, -as olein, stearin, the fatty matter of the brain and nerves, acetic, oxalic, benzoic, and lactic acids, sugar of milk, sugar of diabetes, picromel, colouring principle of the bile, and that of other solids and liquids, &c.

a. Organic Elements that contain Nitrogen.

1. Protein. Modern researches appear to have shown, that the chief proximate principles of animal tissues, and those that have been regarded as highly nutritious among vegetables, have almost identically the same composition; and are modifications of a principle to which Mulder-its discoverer-gave the name Protein. If animal albumen, fibrin, or casein, be dissolved in a moderately strong solution of caustic potassa, and the solution be exposed for some time to a high temperature, these substances are decomposed. The addition of acetic acid to the solution causes, in all three, the separation of a gelatinous translucent precipitate, which has exactly the same character and composition, from whichsoever of the solutions it is obtained. It may be procured, too, from globulin of blood, and from vegetable albumen.2

The chemical relations of protein, especially in regard to oxygen, are full of interest. The products of its oxidation, binoxide and tritoxide of protein, occur constantly in the blood. They are formed in the lungs from fibrin; which, in a moist state, possesses the property of absorbing oxygen. Fibrin, oxidized in the lungs, is, according to Mulder, the principal-if not the only-carrier of the oxygen of the air in the blood to the tissues; and it is from this substance especially, that the secretions are formed. In inflammatory conditions, a much larger quantity of protein in an oxidized state is contained in the blood than in health; and this, according to Mulder, gives occasion to the buffy coat.3

The following substances may be regarded as modifications or combinations of protein. They are composed of it and of a small quantity of phosphorus, or of sulphur, or both.4

'Rapport de l'Académie Royale de Médecine, Juillet, 1841; Taylor's Medical Jurispru dence, by Dr. Griffith, p. 133, Philad., 1845; and Simon, Animal Chemistry, Sydenham Soc. edit., p. 4, Lond., 1845, or Amer. edit., Philad., 1845.

'Liebig, Animal Chemistry, Gregory's and Webster's edit., p. 100. Cambridge, 1842. 3 Simon's Animal Chemistry, Sydenham Soc. edit., p. 12, London, 1845; or American edit., Philadelphia, 1845. 4 Henle, op. cit., p. 31.

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