vered in the year 1803, in the medulla spinalis of the horse, bullock, sheep, hog, and dog; and should it appear to you deserving of being laid before the Royal Society, I shall feel myself particularly obliged, by having such an honour conferred upon me. the ventricles of the brain, Upon tracing the sixth ventricle of the brain, which cor- communicatresponds to the fourth in the human subject, to its appa- ing with one of rent termination, the calamus scriptorius, I perceived the appearance of a canal, continuing by a direct course into the centre of the spinal marrow. To ascertain with accuracy whether such structure existed throughout its whole length, I made sections of the spinal marrow at different distances from the brain, and found that each divided portion exhibited an orifice with a diameter sufficient to admit a large sized pin; from which a small quantity of transparent colourless fluid issued, like that contained in the and containing ventricles of the brain. The canal is lined by a membrane a fluid, resembling the tunica arachnoidea, and is situate above the fissure of the medulla, being separated by a medullary layer it is most easily distinguished where the large nerves are given off in the bend of the neck and sacrum, imperceptibly terminating in the cauda equina. Having satisfactorily ascertained its existence through the A continuate whole length of the spinal marrow, my next object was to tube the whole length of the discover whether it was a continued tube from one extremity spinal marrow. to the other this was most decidedly proved, by dividing the spinal marrow through the middle, and pouring mercury into the orifice where the canal was cut across, it passed in a small stream with equal facility towards the brain (into which it entered), or in a contrary direction to where the spinal marrow terminates. nication with By many similar experiments, I have since proved, that a The fluid has free communication of the limpid fluid, which the canal a free commu. contains, is kept up between the brain and whole extent of the brain, spinal marrow. I have consulted the most celebrated authors on comparative anatomy, but do not find any such structure of those parts described; and as it is not known to you, I may presume, that it has not been before taken notice of. I have the honour to be, Sir, your obedient faithful servant, Veterinary College, Nov. 26, 1808. WM. SEWELL. Beef boiled in XVII. Note on the Alteration, that Air and Water produce in Flesh. I Boiled some beef, renewing the water from time to time, water repeat, till the water no longer afforded a precipitate with tannin. edly, exposed to the actiou I then suspended it in a glass cylinder filled with atmoof air, spheric air, which rested on a plate filled with water. After a few days the oxigen was found to be converted into carbonic acid the interior of the cylinder was filled with a putrid and again boil. smell: the beef, subjected to ebullition, again afforded a ed. This done re- Beef and cheese separately distilled. pretty copious precipitate with tannin: the boiling was repeated, till tannin ceased to render the water turbid: and the beef, having almost entirely lost its smell, was replaced in the same apparatus. The operation was repeated several times, and the fol lowing were the results. The alteration of the atmospherie air, and the emission of the putrid smell, gradually slackened: the quantity of gelatine formed progressively diminished: the water on which the vessel rested gave but slight indications of ammonia throughout the whole process: when I terminated it, no putrid smell was perceptible, but a smell resembling that of cheese: and in fact the animal substance, which scarcely retained any fibrous appearance, had not only the smell, but precisely the taste of old cheese. I distilled separately equal weights of beef and Gruyere cheese, employing two glass bodies, each of which commu nicated with a tube opening under water. The operation was conducted so as to decompose the two substances as far as possible, and retain all the ammonia, that was evolved. Less ammonia On comparing the quantities of ammonia, that afforded by the cheese was to that of the beef nearly as 19 to 24: whence it appears, that a distinguishing characteristic of the caseous substance is to contain less nitrogen than flesh. from the cheese. * Journal de Physique, Vol. LXV, p. 466. If any inference be drawn from experiments so in- Conclusion, may complete as the preceding, it would appear: in animal sub 1. That the gelatine obtainable from an animal sub- Gelatine not stance does not exist completely formed in it; but that, wholly formed when this substance has been exhausted by the action of stances. water, more may be formed by the action of the air, the oxigen of which combines with the carbon, while a portion of the substance, that was before solid, becomes gelatinous, as a solid part of a vegetable becomes solid by the action of the air. stances. It must be remarked however, that the property of pre- Tannin affects cipitating with tannin belongs to substances, that have very different subdifferent qualities in other respects. I have found, that the decoction of Gruyere cheese formed a copious precipitate with tannin. 2. That nitrogen enters into the composition of the pu- Putrid gas. trid gas, forming no doubt with hidrogen a combination less stable than ammonia, or perhaps taking an intermediate state; but, when its proportion is diminished to a certain degree, it is more strongly retained by the substance, and ceases to produce putrid gas. This substance, which is characterized by the putrid smell, appears to be rather a very evaporable compound, that unites with all gasses, like other elastic vapours, than a permanent gas. 3. Since the caseous part has less nitrogen than most Caseous mad. other animal substances, we may conjecture, that this part ter. becomes more and more animalized during life, acquiring a greater proportion of nitrogen and hidrogen; which may be explained by the more intimate combination of the oxigen and hidrogen, that enter into its composition, and by the separation of carbon in the act of respiration; so that the last term of chemical action during life is the production of Ureeuree, agreeably to the opinion of Mr. Fourcroy*. * Syst. des Connoiss. Chim. tom. 10, p. 165; or English ed. Vol. X, P. 231. XVIII. Analysis of a Schist in the Environs of Cherbourg, taken from the Excavations made in Bonaparte Harbour. By Mr. BERTHIER, Mine Engineer*. The rock de CONSIDERED separately, and in small masses, this scribed. Afalysis. rock has all the characters of the primitive formation. It is of a dirty green colour, and has the greasiness and lustre of talc, though in a very slight degree. Its texture is slaty, and a multitude of little grains of crystalline quartz, dis seminated between its laminæ, are visible to the naked eye. Some have a laminated fracture, and are probably feldspar: we may unquestionably however consider it as of intermediate formation from its situation. In fact Mr. Descotils has observed, that it contains blocks of granite, frequently pretty large and rounded; and that it alternates with ancient breccias well characterized, talky and argillaceous schists, &c. It would have been impossible to separate the quartz, mixed with it, whatever pains were taken. Besides, the person who sent it to the laboratory desired, that it should be analysed as it was. Five grammes [77 grs.] were fused with double their weight of caustic potash, dissolved in pure muriatic acid, evaporated to dryness, and the silex separated. The liquor being filtered, and tested with sulphuric acid and sulphuretted hidrogen, gave no precipitate. Hidrosulphuret of ammonia formed in it a black precipitate. Being filtered, oxalate of ammonia, afterward poured into the liquor, scarcely rendered it turbid; and potash precipitated a small quantity of magnesia. The sulphurets having been redissolved in nitromuriatic acid, the whole was precipitated afresh by saturated carbonate of potash. Nothing remained in the liquor, which proved the absence of manganese. Lastly the alumine and iron were separated by caústic potash. Journal des Mines, vol. XXI, p. 315. The |