BRA

BRA

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feme traces of phofphat of lime and foda.iBrain, either in its natural ftate or gently driedwithout decompofition, unites very readily withwater by rubbing, and forms an opake uniformomul five mafs, which froths ftrongly by agitation,and does not feparate from the water by filtration.In this it much refembles a folution of foap inwater, but differs from the genuine foaps incontaining no alkali, and hence it will not turnvegetable blues into green.

This emulfion of brain when heated nearlyto boiling readily coagulates, and depofits itscontents in white curdy grains. The clear liquidmixed with lime-water gives a precipitate ofphofphat of lime, and hence contains a phof-phated fait in folution. Acids and all calcareousfalts added to the cerebral emulfion fpeedilycurdle it. If an acid is employed, the clearliquor remaining after the coagulation containslime, foda and ammonia, all united with theacid.

The nitric acid when dilute only coagulatesthe cerebral emulfion, but when concentrated itproduces an effervefcence, with evolution ofmuch azotic gas, violent intumefcence, heat,and fubfequent produ£lion of nitrous gas, car-bonic acid, and ammonia. The refidue nowcontains a quantity of oxalic acid, one of theufual products of the diftillation of nitric acidwith almoft any animal matter.

Muriatic acid limply coagulates the emulfionof brain, without inducing any very ftrikmgchemical change.

The cauftic fixed alkalies even when cold,and much more when hot, unite fpeedily withbrain into a foapy mafs, at the fame time difen-gaging much ammonia.

Under the article Adipocire was noticed thefingular action of alcohol and the feparation ofa peculiar cryftalline matter. A fimilar circum-ftance occurs here. When brain gently driedover a ilove, or fir ft mixed with water, coagu-lated by an acid, and the coagulum dried, isdigefted in a boiling heat with about twice itsweight of alcohol, a folution is effected, whichon cooling depofits a number of yellowilh whitecryftalline blades. It requires two or three fuc-ceffive digeftions with frelh alcohol entirely toexhauft this cryftalline matter. Dried brainlofes in the procefs about five-eighths of itsweight, however on evaporating the alcoholicfolution, no more than half the above quantityis collected, fo that the remainder is probablyonly water intimately combined with the fub-ftance of brain, and not to be expelled by theprevious drying. This fingular cryftalline matter

crufhes under the finger with a kind of greafyconfiftence, is not melted, but only foftened inthe heat of boiling water; and .when furtherheated it blackens, melts, and gives out a burntand ammoniacal fmell. In this rel'pect it differsfrom fpermaceti, which melts at 140° and coolsagain unchanged. Adipocire, to which alfo ithas been likened, melts unaltered at about 83°.After the alcoholic folution of brain has de-pofited on cooling all the cryftalline matter, thefolution, evaporated, will give more of the fame,but fomewhat laltilh and of a foapy confiftence.This matter may be united with water by rub-bing, into a kind of emulfion, which reddenslitmus. A long maceration of brain in coldalcohol will diffolve a fimilar cryftalline matter,and hence it is often found depofited in oldfpirituous anatomical preparations of the brainand nerves.

The fubftance of brain bears on the wholea confiderable refemblance to albumen reducedto a kind of faponaceous Hate, perhaps by unionwith ammonia and much water; but the theoryof the production of this cryftalline matter isvery obfeure. Though it much refembles fper-maceti, adipocire, and ftill more the cryftallinematter of biliary calculi (deferibed under thatarticle) it fomewhat differs from them all, par-ticularly in being difficult of fufion. Its natureis confiderably like that of a concrete oil, andhence Thouret was led to endeavour to extractoil from the brain by ftrong prefiure, but with-out any fuccefs.

The fpontaneous change which brain under-goes by putrefaction, and the very flow decom-pofition of this organ by fpontaneous changeare very fingular circumftances, fince it is wellknown to anatomifts how great a lofs of ftrengthand cohefion in the texture of brain is fufferedby keeping a very fhort time after death. Yetthis fame fubftance after this firft change oftexture appears to be perhaps the molt inde-ftruclible of all the foft parts of the animalbody. The memorable obfervations of Thoureton the exhumation of the burying ground ofLes Innocents, at Paris , put this beyond a doubt.This obferver remarks, that the bodies containedin this vaft cemetery were found in differentftates; the greater number of them (whichwere thofe that had lain in heaps in the com-mon receptacles of twelve or fifteen hundredcorpfes) were moftly converted to a kind ofwhitifh foap, retaining the form of the differentparts of the body. In all thefe the brain wasin a ftate of very perfe£t prefervation, and ot!opening the fcull it was found in pretty largex 2