Alobert, in his Precis Pratique et Theoretique sur les Maladies de la Peau, Paris, 1810, tom. i., p. 344, Art. VIII., had published two analyses of herpetic eruptions, and it gave me great pleasure to see that they completely coincided with my own. He discovered an uncombined acid in the scales, which he showed to be phosphoric acid. In the leprous part he found no uncombined acid, but carbonate of lime.

III. Nails.

The nails exhibit nearly the same properties as the epidermis. They consist of the same materials, scarcely differing in their pro portions. The insoluble portion possesses the characters of indurated albumen.

IV. Horns of Black Cattle.

Under this name I reckon the horny sheaths which artists employ in the manufacture of a variety of articles which may be considered as indispensable necessaries of life, as combs, knife-handles, watchmen's horns, boxes, sheaths, &c. They must not be confounded with the bony horns, as those of the hart, &c. which are easily renewed when the animal drops them, and which are composed of quite different materials. These last contain generally much gelatine and earth of bones. The horny sheaths remain attached to animals during the whole of their lives. Sometimes, indeed, they lose them in consequence of disease. Of this the horn of a cow, with which I made my first experiments, furnishes us with an example. The composition of these bodies is quite different from that of true horns, and perhaps it deserves attention that, besides the uncombined acid which I discovered in the epidermis, they contain likewise a peculiar liquid oil. Their composition indicates clearly that they must be considered as indurations and extensions of the epidermis.

(a) From 4 to 6 oz. of horn shavings were mixed with 12 oz. of water, and distilled. The distillation was stopped when 5 oz. of the water had come over. The liquid which had come over was milky, and had a very strong smell of horn, while what remained in the retort was free from smell. Even after an interval of some days I could observe no drops of oil floating on the water, but the matter which occasioned the smell of horn had subsided, under the form of a greyish-white cloud. After 8 or 14 days some flocks subsided, but the cloud remained unaltered.

This holds both with the horns of cows and oxen.

(b) Fifty grains of the fine shavings of a cow's horn were boiled for an hour in at least 12 oz. of water, and the water was renewed in proportion as it evaporated. By this means it was deprived of four grains of its weight. The concentrated solution did not in the least gelatinize. It reddened litmus paper, and had a very sharp salt taste. Alcohol, and the solutions of barytes, acetate of lead,"

oxalic acid, and other acids, caused a precipitate in it, and by repeated evaporation mucus was separated.

(c) The undissolved portion did not swell in water, like epidermis and the nails. When heated, it softened, and at last melted. Nitric acid dissolves it completely, and forms much oxalic acid. The alkaline leys likewise dissolve it. When distilled, it gives the same products as the epidermis, without a trace of acid.

(d) Alcohol dissolves about one per cent. of fat, and likewise some animal matter (osmazom).

(e) When the horn is incinerated it leaves scarcely per cent. of ash, which is white, and composed of the same constituents as the epidermis.

A hundred parts of the horns of black cattle, then, are composed of

Indurated albumen, possessing much of the
characters of mucus

Gelatinous mucus, with an animal matter
thrown down by nutgalls (osmazom?)

Lactic acid

Lactate of potash

Sulphate, muriate, and phosphate of potash
Phosphate of lime

Trace of oxide of iron

Ammoniacal salt

Fat about....

}

90

} s

1

A peculiar volatile substance, which thickens more rapidly than volatile oil, and has the smell of horn.

Observations.

The presence of an essential oil in the animal kingdom, if we are to judge from the experiments hitherto made, is uncommon. The horny sheaths of animals arrange themselves under that genus of bodies which, like plants, give an essential oil on distillation. Ants, likewise, belong to the same genus. This volatile matter of horns, however, is distinguished from proper oil by not collecting in drops when the liquid containing it is allowed to cool. It is uncommonly volatile, and is separated from the horn by simple digestion in water.

In the horns of black cattle I first detected the uncombined acid, which at times is likewise combined with potash. In all probability no combination of this acid with lime occurs in horns. At least when an acid was poured upon the washed ash, I could perceive no effervescence. Even if such a compound exist, it must be much smaller in quantity than the phosphate of lime. These observations led me to conjecture that the same acid might probably be contained in bones. But experiment did not confirm this conjecture; for in bones quite fresh, and neither boiled nor exposed to a red heat, I observed merely carbonate and phosphate of lime.

V. Hoof of the Horse.

The hoof of the horse (either what is called the quick or the sole may be employed) possesses all the characters of horn.

When it is distilled with water, a very fetid liquid is obtained, which contains no perceptible portion of solid matter.

The only other difference which can be perceived is, that the insoluble matter approaches much nearer to caseous albumen than to mucus. When subjected to putrefaction, it assumes exactly the nature of cheese.

The hoof contains no true gelatine. I found no trace of acid in it; and it may be asked whether this substance has been really always wanting to the hoof, or whether it has been abstracted in consequence of the constant moisture to which the hoof is exposed? This may happen the more readily, as Nature has given to the hoof no portion soever of fat, by which it might be defended from the solvent power of the water.

VI. Horny Excrescence of a Pigeon.

This example, perhaps the only one known of a similar monstrosity, is to be seen in the Royal Museum. The pigeon, which was full grown, and of the size of a common pigeon, was sent from Nordhausen by Mr. Surgeon-General Görcke. The excrescence had exactly the form of the horn of a he-goat. It grew out of one side of the back, from which the tail feathers had fallen, and had a greater weight than the whole pigeon.

The substance of this horn has a somewhat smutty wax-yellow colour. It is less transparent than horn; and in respect of hardness, is intermediate between wax and horn.

Through the goodness of Professor Rodolphi, I obtained a small portion, which we cut from the hind end in such a manner that the loss would not be perceived by those who examined this extraordinary monster.

By boiling in water, there was dissolved a small portion of gelatinous mucus precipitated by infusion of nutgalls, and likewise traces of alkaline sulphate, muriate, and phosphate.

Alcohol separated a fatty matter, as it did from the horns of black cattle. Cold water produced no effect. When incinerated, it left a very small portion of ashes, which contained an alkali, the above-named salts, phosphate of lime, and gypsum. The undissolved portion of this horny excrescence, which amounted at least to 94 per cent., possessed the properties of insoluble mucus.

ARTICLE III.

On the Chemical Action of Bodies on each other when triturated together. By H. F. Link.*

In a dissertation on Berthollet's theory of affinity (Gehlen's Journal für die Chemie und Physik, vol. iii. p. 240), among other arguments against Berthollet's theory, I stated that bodies are decomposed by merely triturating them together; though, according to Berthollet, this decomposition is only the consequence of a difference in the solubility or volatility of bodies. At that time I paid little or no attention to the water of crystallization, because this water is in the state of a solid body, and cannot act as a medium of solution and the assertion that all decomposition is the result of easy or difficult solubility, in as far as solubility is concerned, is essential to Berthollet's doctrine of affinity. On that side the theory requires quite other determinations.

It must further be admitted by the supporters of Berthollet's theory that a chemical combination is produced by the trituration of dry bodies together. This combination agrees completely with the theory, and takes place in different proportions. Whether a decomposition takes place depends upon the presence of an easily soluble portion in the compound. Sulphate of potash and muriate of barytes dissolved in water unite together; but the insoluble portion, the sulphate of barytes, separates itself. When I triturate together muriate of barytes and sulphate of copper deprived of its water of crystallization, a combination of all the ingredients of course takes place. But why does alcohol produce no change in it, since it contains muriate of copper, a body easily soluble in that liquid? Similar questions may be put in many other cases, which must at least alter the theory.

But I leave the considerations respecting Berthollet's theory, which a more accurate knowledge of facts have suggested. The experiments on the trituration of bodies with each other ought not, in my opinion, to be entirely neglected, as perhaps some general consequences respecting the chemical action of bodies on each other may be drawn from them.

Muriate of lime and sulphate of copper, both dry, and the latter heated on a metal plate till it fell down in the state of a white powder, remained, after being triturated together, quite white. Absolute alcohol (when I speak of this liquid hereafter, I always mean it in that state) gave the powder a yellow colour. Water rendered it blue. If we triturate crystallized sulphate of copper with muriate of lime, the powder has a yellow colour. Muriate of

* Translated from Schweigger's Journal, vol. xiv. p. 193, October, 1815.

barytes and anhydrous sulphate of copper triturated together remain white. Alcohol does not alter the colour. Water gives it a blue colour. I must here put the reader in mind that muriate of copper with little water is yellow; but, when united with much water, blue.

In these experiments the difference between muriate of lime and muriate of barytes consists in this, that the former is soluble in alcohol, while the latter is insoluble in that liquid. Solution, then, is necessary to chemical action. The water of crystallization of sulphate of copper acts entirely as uncombined water, and the chemical action of the water is not the consequence of its liquidity, but is peculiar to it.

Acetate of lead in crystals, and anhydrous sulphate of copper, when triturated together, remain white, and do not alter one another. But when acetate of lead and crystals of sulphate of copper are triturated together, the mixture assumes immediately a fine green colour. Alcohol gives to the white powder a shade of green,. and water renders it much more green. As acetate of lead in crystals decomposes crystallized sulphate of copper, but not the anhydrous sulphate, it is probable that it contains no water of crystallization, at least none in a state capable of acting. Acetate of lead is soluble in alcohol, though only in small quantity.

Acetate of lead and burnt alum just heated, and scarcely cooled, being triturated together, produced no alteration on each other, and afterwards liquefied very slowly when left in an open vessel. But when the burnt alum had been kept for some time in a vessel not very well stopped, it very soon became liquid when triturated with acetate of lead. The moisture of the atmosphere, therefore, does not act directly as a medium of decomposition, but only when it has been absorbed by a solid body, and deprived of its fluidity.

One part of muriate of lime and two parts of sulphate of potash, being triturated together, became at first somewhat moist, but gradually dried again when left exposed to the air. The taste at first was that of muriate of lime, but it became gradually weaker, and at last assumed a salt taste.

Prussiate of potash and sulphate of copper, both heated till the water of crystallization was evaporated, when triturated together, remained white. Alcohol did not alter the colour. Water rendered it reddish-brown. If we take crystallized sulphate of copper instead of anhydrous, the mixture on trituration assumes a reddish colour. The same thing takes place when anhydrous sulphate of copper is triturated with crystallized prussiate of potash.

Anhydrous acetate of copper, being triturated with anhydrous prussiate of potash, produced a green colour. Alcohol did not alter the colour; but when left for some days in an open vessel, the colour became lavender-blue. Water rendered the colour reddishthe reader in mind that cold alcohol dissolves little or no acetate of copper.

brown. I may here put

Carbonate of ammonia and anhydrous acetate of copper, when