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bullocks, selected, as nearly as possible, of the same age and vigor, and subjected to comparative experiment. They were all supplied with an abundance of nutritious food; but three of them (lot No. 1) received also a little over 500 grains of salt each per day. The remaining three (lot No. 2) received no salt, but in other respects were treated like the first. The result of these experiments is given by Boussingault as follows:

"Though salt administered with the food has but little effect in increasing the size of the animal, it appears to exert a favorable influence upon his qualities and general aspect. Until the end of March (the experiment began in October) the two lots experimented on did not present any marked difference in their appearance; but in the course of the following April, this difference became quite manifest, even to an unpractised eye. The lot No. 2 had then been without salt for six months. In the animals of both lots the skin had a fine and substantial texture, easily stretched and separated from the ribs; but the hair, which was tarnished and disordered in the bullocks of the second lot, was smooth and glistening in those of the first. As the experiment went on, these characters became more marked; and at the beginning of October the animals of lot No. 2, after going without salt for an entire year, presented a rough and tangled hide, with patches here and there where the skin was entirely uncovered. The bullocks of lot No. 1 retained, on the contrary, the ordinary aspect of stall-fed animals. Their vivacity and their frequent attempts at mounting contrasted strongly with the dull and unexcitable aspect presented by the others. No doubt, the first lot would have commanded a higher price in the market than the second."

Chloride of sodium acts also in a favorable manner by exciting the digestive fluids, and assisting in this way the solution of the food. For food which is tasteless, however nutritious it may be in other respects, is taken with reluctance and digested with difficulty; while the attractive flavor which is developed by cooking and by the addition of salt and other condiments in proper proportion excites the secretion of the saliva and gastric juice, and facilitates consequently the whole process of digestion. The chloride of sodium is then taken up by absorption from the intestine, and is deposited in various quantities in different parts of the body.

It is discharged with the urine, mucus, cutaneous perspiration,

1 Chimie Agricole, p. 271. Paris, 1854.

&c., in solution in the water of these fluids. According to the estimates of M. Barral,' a small quantity of chloride of sodium dis appears in the body; since he finds by accurate comparison that all the salt introduced with the food is not to be found in the excreted fluids, but that about one-fifth of it remains unaccounted for. This portion is supposed to undergo a double decomposition in the blood with phosphate of potass, forming chloride of potassium and phosphate of soda. By far the greater part of the chloride of sodium, however, escapes under its own form with the secretions.

3. CHLORIDE OF POTASSIUM.-This substance is found in the muscles, the blood, the milk, the urine, and various other fluids and tissues of the body. It is not so universally present as chloride of sodium, and not so important as a proximate principle. In some parts of the body it is more abundant than the latter salt, in others less so. Thus, in the blood there is more chloride of sodium than chloride of potassium, but in the muscles there is more chloride of potassium than chloride of sodium. This substance is always in a fluid form, by its ready solubility in water, and is easily separated by lixiviation. It is introduced mostly with the food, but is probably formed partly in the interior of the body from chloride of sodium by double decomposition, as already mentioned. It is discharged with the mucus, the saliva, and the urine.

4. PHOSPHATE OF LIME. This is perhaps the most important of the mineral ingredients of the body next to chloride of sodium. It is met with universally, in every tissue and every fluid. Its quantity, however, varies very much in different parts, as will be seen by the following list:

QUANTITY OF PHOSPHATE OF LIME IN 1,000 PARTS IN THE
Enamel of the teeth.

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Muscles
Blood
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It occurs also under different physical conditions. In the bones, teeth, and cartilages it is solid, and gives to these tissues the resistance and solidity which are characteristic of them. The calcareous salt is not, however, in these instances, simply deposited mechanically in the substance of the bone or cartilage as a granular powder, but is intimately united with the animal matter of the tissues, like

In Robin and Verdeil, op. cit., vol. ii. p. 193.

a coloring matter in colored glass, so as to present a more or less homogeneous appearance. It can, however, be readily dissolved. out by maceration in dilute muriatic acid, leaving behind the animal substance, which still retains the original form of the bone or cartilage. It is not, therefore, united with the animal matter so as to lose its identity and form a new chemical substance, as where an acid combines with an alkali to form a salt, but in the same manner as salt unites with water in a saline solution, both substances retaining their original character and composition, but so intimately associated that they cannot be separated by mechanical

means.

In the blood, phosphate of lime is in a liquid form, notwithstanding its insolubility in water and in alkaline fluids, being held in solution by the albuminous matters of the circulating fluid. In the urine, it is retained in solution by the bi-phosphate of soda.

Fig. 1.

In all the solid tissues it is useful by giving to them their proper consistence and solidity. For example, in the enamel of the teeth, the hardest tissue of the body, it predominates very much over the animal matter, and is present in greater abundance there than in any other part of the frame. In the dentine, a softer tissue, it is in somewhat smaller quantity, and in the bones smaller still; though in the bones it continues to form more than one-half the entire mass of the osseous substance. The importance of phosphate of lime in communicating to bones their natural stiffness and consistency may be readily shown by the alteration which they suffer from its removal. If a long bone be macerated in dilute muriatic acid, the earthy salt, as already mentioned, is entirely dissolved out, when the bone loses its rigidity, and may be bent or twisted in any direction without breaking. (Fig. 1.)

Whenever the nutrition of the bone during life is interfered with from any pathological cause, so that its phosphate of lime becomes deficient in amount, a softening of the osseous tissue is the consequence, by which the bones yield to external pressure, and become more or less distorted. (Osteomalakia.)

[graphic]

FIBULA TIED IN A KNOT, after maceration in a dilute acid. (From a specimen in the museum of the College of Physicians and Surgeons.)

After forming, for a time, a part of the tissues and fluids, the

phosphate of lime is discharged from the body by the urine, the perspiration, mucus, &c. Much the larger portion is discharged by the urine. A small quantity also occurs in the feces, but that is probably only the superfluous residue of what is taken in with the food.

5. CARBONATE OF LIME.-Carbonate of lime is to be found in the bones, and sometimes in the urine. The concretions of the internal ear are almost entirely formed of it. It very probably occurs also in the blood, teeth, cartilages, and sebaceous matter; but its presence here is not quite certain, since it may have been produced from the lactate, or other organic combination, by the process of incineration. In the bones, it is in much smaller quantity than the phosphate. Its solubility in the blood and the urine is accounted for by the presence of free carbonic acid, and also of chloride of potassium, both of which substances exert a soluble action on carbonate of lime.

6. CARBONATE OF SODA.-This substance exists in the bones, · blood, saliva, lymph, and urine. As it is readily soluble in water, it naturally assumes the liquid form in the animal fluids. It is important principally as giving to the blood its alkalescent reaction, by which the solution of the albumen is facilitated, and various other chemico-physiological processes in the blood accomplished. The alkalescence of the blood is, in fact, necessary to life; for it is found that, in the living animal, if a mineral acid be gradually injected into the blood, so dilute as not to coagulate the albumen, death takes place before its alkaline reaction has been completely neutralized.'

The carbonate of soda of the blood is partly introduced as such with the food; but the greater part of it is formed within the body by the decomposition of other salts, introduced with certain fruits and vegetables. These fruits and vegetables, such as apples, cherries, grapes, potatoes, &c., contain malates, tartrates, and citrates of soda and potass. Now, it has been often noticed that, after the use of acescent fruits and vegetables containing the above salts, the urine becomes alkaline in reaction from the presence of the alkaline carbonates. Lehmann' found, by experiments upon his own person, that, within thirteen minutes after taking half an ounce

Cl. Bernard. Lectures on the Blood; reported by W. F. Atlee, M. D. Philadelphia, 1854, p. 31.

2 Physiological Chemistry. Philadelphia ed., vol. i. p. 97.

of lactate of soda, the urine had an alkaline reaction. He also observed that, if a solution of lactate of soda were injected into the jugular vein of a dog, the urine became alkaline at the end of five, or, at the latest, of twelve minutes. The conversion of these salts into carbonates takes place, therefore, not in the intestine but in the blood. The same observer' found that, in many persons living on a mixed diet, the urine became alkaline in two or three hours after swallowing ten grains of acetate of soda. These salts, therefore, on being introduced into the animal body, are decomposed. Their organic acid is destroyed and replaced by carbonic acid; and they are then discharged under the form of carbonates of soda and potass.

7. CARBONATE OF POTASS.-This substance occurs in very nearly the same situations as the last. In the blood, however, it is in smaller quantity. It is mostly produced, as above stated, by the decomposition of the malate, tartrate, and citrate, in the same manner as the carbonate of soda. Its function is also the same as that of the soda salt, and it is discharged in the same manner from the body.

8. PHOSPHATES OF MAGNESIA, SODA, AND POTASS.-All these substances exist universally in all the solids and fluids of the body, but in very small quantity. The phosphates of soda and potass are easily dissolved in the fluids, owing to their ready solubility in water. The phosphate of magnesia is held in solution in the blood by the alkaline chlorides and phosphates; in the urine, by the acid. phosphate of soda.

A peculiar relation exists between the alkaline phosphates and carbonates in different classes of animals. For while the fluids of carnivorous animals contain a preponderance of phosphates, those of the herbivora contain a preponderance of the carbonates: a peculiarity readily understood when we recollect that muscular flesh and the animal tissues generally are comparatively abundant in phosphates; while vegetable substances abound in salts of the organic acids, which give rise, as already described, by decomposition in the blood, to the alkaline carbonates.

The proximate principles included in the above list resemble

1 Physiological Chemistry, vol. ii. p. 130.

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