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5. It dissolves in hot alcohol, leaving only a few flocks of animal matter, which had been dissolved in the first operation by means of ihe water contained in the brain. During the cooling of the alcohol the greatest part of this matter precipitates with all its usual characters: 20 parts of alcohol at 36 degrees are sufficient to dissolve one part of this matter.
3. When exposed to the sun this matter acquires a yellow color, nearly similar to that of the fatty matter which is obtained by the evaporation of tire alcohol, after it has deposited the fatty matter, the properties of which we are describing. I do not know the reason of this phenomenon.
4. A portion of this matter, which had been dissolved several times in alcohol to separate the last remains of the animal matter "which it contained, was burnt in a platinum crucible. The combustion took place very jseadily, and was accompanied by a great deal of flame and smoke. The charry residue washed with distilled water communicated to that fluid a very distinct acidity, and the property of precipitating lime-water.
The singular result of this operation, which announced unambiguously the presence of phosphoric acid, made me suspect that this fatty matter contained phosphoric acid, or phosphate of ammonia, "the base of which might have been volatilized by heat, though this last opinion was not very probable. However, to determine the point, I made the following experiments:—
1. I mixed the fatty matter with distilled water, and observed with surprise that it formed with that fluid a kind of emulsion, and did not separate from it. At the same time, I observed that this emulsion possessed no acid properties, and did not alter the color of tincture of litmus.
2. I mixed it with a solution of caustic potash, and perceived no indication of the. presence of ammonia. Even a boiling heat did not develope the smallest trace of this alkali. In this experiment I was very much surprised to perceive, that though I had employed a quantity of potash more than sufficient to dissolve a quantity of tallow, more than I employed, yet the solution did not take place; and the mixture remained as milky as if water had been employed instead of potash.
I think we may conclude from these experiments that the fatty matter from the brain contained neither phosphoric acid nor phosphate of ammonia, and that the acid which appears after the combustion had another origin.
3. A hundred parts of the fatty matter of the brain were heated in a platinum crucible, with 200 parts of potash and a little water. The mixture did not melt; but, on .the contrary, became harder, which would not have happened if the substance in question had been real tallow. When the humidity was dissipated it assumed a. brown color, took fire, emitted an odor of burning grease, and gav^ out a great deal of smoke. The residue of this operation was washed with distilled water; the liquid being saturated with nitric acid, and boiled, gave, when mixed with lime-water, a flocky precipitate, which
I 2 was was phosphate of lime, and which weighed, when dry, the tenth part of the mass employed.
4. A hundred parts of the same matter thrown successively into melted nitre took fire with great facility, producing scarcely any smoke; the whole was destroyed, and not the smallest trace of charry matter remained. The residue of this operation, treated in the same manner as the preceding, gave the same quantity of phosphate of lime.
What conclusion can be drawn from these experiments, except that there is phosphorus combined with the fatty matter of the brain, and which dissolved in alcohol at the same time with the fatty matr ter s We find in the residue after combustion neither phosphate of lime nor phosphate of magnesia. The alkaline phosphates would have found enough of water in the brain to remain in solution in the alcohol, and not to precipitate when the liquid cools. Accords ingly we find phosphate of potash, superphosphate of lime and of magnesia, in the residue of the alcohol evaporated, which had been digested with the cerebral matter. We must therefore admit the existence of phosphorus in the brain, as well as in the roes of fishes, where it was discovered by Fourcroy and me. The proportion of it, indeed, is very small; for, from the quantity of phosphate of lime which I obtained in the preceding experiments, I estimate its quantity not to exceed -r^g-ths of a part: but if we subtract the humidity of the brain, and only consider the dry residuum, in that case the phosphorus may be considered as amounting to about ■j^th part of the whole.
Though the substance whose properties have been described in, this section has more analogy with tallow aud fat than with any other class of bodies, yet it ought not to be confounded with ordinary fat. It differs from it principally by its solubility in alcohol, its capacity of crystallizing, its viscidity, its inferior fusibility, and the blackcolor which it assumes in melting. Thus, though we class it among fatty bodies, we ought to consider it as a particular and • new species.
Sect. V.—Of the fatty matter of the brain which remains in solution in the alcohol after its cooling.
We have observed before, that after the alcohol digested with the brain had deposited its fatty matter, it remained of a green color; and that the third, the fourth, and even the fifth, portion of alcohol, which had been digested on the same portion of brain, had a sapphire-blue color. In order to discover the coloring matter, we distilled this alcohol. The following are the observations that we made:—
The green and blue color is'not destroyed by the evaporation of the alcohol, as long as any of the alcohol remains; but as soon as the whole is driven off, the matter acquires a yellow color, of more or less intensity. Neither the alkalies nor acids change these colors.
When these operations are performed on the first and second portions of alcohol which have been digested on the same quantity of brain, we see, as has been mentioned above, an oily fluid of a yellow color precipitate itself to the bottom of the aqueous fluid derived from the humidity of the brain. But this effect does not take place with the last portions of alcohol, because they contain no more water.
The liquid, at the bottom of which this fatty matter collects, has likewise a yellow color, a taste of the juice of meat, and slightly sweetish, and it gives marks of acidity. While this liquor is hot, the matter remains quite distinct, and seems to have some consistence; but by cooling, or on the addition of a little water, it absorbs humidity, becomes opake, and so mixed with the water that it cannot be separated. We must therefore take advantage of the favorable moment to make this separation in the proper manner.
From these remarks it is obvious that hot water must be employed to wash this substance, and to free it from the soluble matters with which it is mixed.
To dry this oil after washing it, we may expose it for some time to the open air, or to a gentle heat.
Let us examine the properties of this matter thus purified, leaving to another section the examination of the water from which it has been separated.
1. It has a reddish brown color, an odor similar to that of the brain itself, but stronger. Hence it is probably this substance which gives its peculiar odor to the brain.
2. Its taste is similar to that of rancid fat.
3. When agitated with cold water it mixes with that liquid, and forms a sort of homogeneous emulsion, which separates only very slowly. The mineral acids, mixed in a certain quantity with this emulsion, immediately precipitate an oily matter, under the form of white opake flocks; and the liquor then passes clear through the filter, which was not the case before. The muriatic acid which lias thus served to coagulate this species of emulsion, lets fall very light white flocks, when mixed with ammonia; but when nitric acid is employed, it neither can be made to precipitate by ammonia nor lime-water.
The infusion of nutgalls likewise coagulates this emulsion.
4. If the water be decanted off as soon as the fatty matter is deposited, and it be left to itself, it putrities, and exhales a fetid odor, indicating the presence of an animal matter.
5. It dissolves in hot alcohol, some light flocks excepted, which do not amount to the hundredth part of it. The greatest part of it separates from the alcohol when it cools, and renders it milky, as would happen to a solution of resin.
6. Exposed on burning coals it melts, blackens, swells up, and emits an odor of burning animal matter, and afterwards that of grease in the state of vapor.
7. When burnt in a platinum crucible, either alone or mixed with potash or nitrate of potash, it always furnishes phosphoric acid, either uncombined or combined with the alkali, according to the process; just as happens to the fatty matter deposited from the alcohol during its cooling. Hence we roust form the same opinion respecting t\ origin of this acid. We must admit the presence of phosphorus i the fatty matter.
From 400 grammes of brain employed in this process we hn\ obtained about 3 grammes of this matter, which amounts to aboi 0 75 of a gramme per cent.
We ought now to inquire in what this substance differs from the which falls spontaneously from the alcohol during its cooling, tli properties of which have been already described.
Though it remains in solution in the cold alcohol, it is not ver soluble in that liquid; for when alcohol, at a boiling temperature is saturated with it, a portion is deposited, as the alcohol cools, ii the form of flocks. In this respect it approaches very near the firs substance. It differs from it by its reddish brown color, by il smaller consistence, by its slight taste of boiled meat which the firs substance has not, and by a greater tendency to crystallization.
This difference is produced by a certain quantity of animal mat ter, of which we shall speak hereafter, and which may be separata from the fatty matter by means of cold alcohol.
Sect. VI.—Of the yellow aqueous liquor which remains after th
separation of the two fatly substances, by cooling and by evapc
rating the alcohol.
When one has deprived the brain, by means of alcohol, of ever thing soluble in that liquid, and separated, by the methods abov< described, the two fatty substances from the alcohol, there remaiu a liquor of a brownish yellow color, which has the taste of thejuici of meat with a little sweetness. This liquid reddeus litmus; and i precipitated by* lime-water, infusion of nutgalls, &c.
To learn the nature of the substances contained in that liquid, w< Jn the first place diluted it with a quantity of distilled water, anc then poured into it lime-water as long as any precipitate continuec to fall. The matter washed and dried in the open air had a yellovi color. When calcined it assumed a black color, owing to the presence of a little animal matter, which is decomposed by the heat.
This substance thus calcined and re-dissolved in nitric acid wa: again precipitated white by ammonia. It was not blackened by exposure to heat, and possessed the characters of phosphate of lime.
After having precipitated, by means of lime, the phosphoric acid contained in the aqueous liquid, we evaporated it to dryness witl the requisite precautions. The matter which it furnished weighed 4-5 grammes (6*9'5 grains troy). In this state it had a reddish brovvr color, was semi-transparent, had a taste similar to the juice of meal with a little sweetness; it dissolved in alcohol with great facility, leaving only some atoms of a saline matter which effervesced with acids.
Exposed to the air it became soft by attracting humidity. A portion of this matter being heated in a platinum crucible, swelled up considerably, and emitted vapors which had the odor of burning animal matter. It left a charcoal, which yielded, when washed with water and the liquid was evaporated, a little pure carbonate of potash.
It follows, evidently, from these experiments, that the aqueous liquid contained ur.comb inert phosphoric acid and phosphate of potash, or perhaps superphosphate of potash and an animal matter, which by its solubility in alcohol and water, by its property of being precipitated by infusion of nutgalls, by its reddish brown color, its deliquescence, its taste and smell of the juice of meat, ought to be regarded as identical with the substance which Rouelle formerly called the saponaceous extract of meat, and to which M. Theuard. has given the name of osmazome.
It is, without doubt, this substance, a portion of which remains with the fatty matter obtained from the alcohol by~ evaporation, which gives it the reddish color, the property of mixing with water, and of emitting the smell of animal matter when burning.
Sect. VII.—Statement of the constituents of the brain soluble in
alcohol. We now know the different substances separated from the brain by alcohol when repeatedly digested upon it. They are,
1. A fatty matter, white, solid, of a satin lustre, and a tenacity not to be found in ordinary tallow or fat.
2. Another fatty matter of a red color, having less consistence' than the preceding, but which seems to differ from it only in consequence of a little osmazome which remains mixed with it.
: 3. An animal matter of a reddish brown color, soluble in water and alcohol, forming with tannin an insoluble combination, having the smell and taste of the juice of meat, and which is certainly the principle at present distinguished by the name of osmazome.
4. Superphosphate of potash, together with some traces of common salt, of which I have not spoken, because it occurs iu all the auimal humors.
Sect. Vllf.—Examination of the part of the brain which U
insoluble in alcohol. 'When we have separated, by repeated digestions in boiling alcohol, every part of the brain soluble in that liquid, there remains a greyish white matter in the form of flocks, which has the appearance of fresh cheese, but differs from that substance by its chemical properties: 400 grammes of fresh brain furnished 31 grammes of this substance.
■ This substance, in drying, assumes a grey.color, a semitransparence, and a fracture similar to that of gum arabic.
Put into water in that state, it absorbs a portion of it, "becomes opake, swells up, and softens. The water dissolves a small portion of it, for it becomes putrid after an interval of some days.
Thus softened, it dissolves readily by the assistance of heat in caustic potash, and during the solution no ammonia is disengaged, as is the case with the curdy portion of milk wheu dissolved in the same manner.