On the chemical pathology of the brain / by Adam Addison.

  • Addison, Adam.
Date:
[1866]
Catalogue details

Licence: Public Domain Mark

Credit: On the chemical pathology of the brain / by Adam Addison. Source: Wellcome Collection.

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    when this is done ten or twelve times the extraction is generally complete, but I have had to do it nearer twenty times; at any rate, it must be done until it is seen by its colour that the ether does not take up any more fat. As it is impossible to remove the dried brain substance from the watch glasses without loss, the quantity to be used must again be weighed. After the fat is thoroughly ex¬ tracted, the ether is evaporated to dryness and the solid residue weighed. The brain substance should not be powdered, but placed in the tube in lumps; otherwise light floating particle will be carried down by the returning ether, and give too high a result. The ad¬ vantage of this method is that a very small quantity of ether suffices to exhaust the brain substance of the fat, and no filtration is required if it is properly done. The brain fats are all soluble in boiling ether; if alcohol is employed, a not inconsiderable quantity of extractive substances which are soluble in this fluid are obtained with the fats. Owing to the want of an accurate method of separation, it did not appear to me that I could undertake the analysis of the fat into cerebrine, cholesterine, &c., with any hope of success. The albu¬ minates, extractives, &c., were reckoned by deducting the amount of fat from the total solids. It has already been stated that Bibra made use of the ether-extract for the determination of the phos¬ phorus. This method did not appear suitable for my purpose. In the first place the quantities of fat extracted were generally very small, and then I was by no means sure that it would contain the absolute amount of phosphorus in the regions from which it was taken. Consequently I preferred to operate on the fresh brain, and then, in order to give an unvarying standard of comparison, to cal¬ culate the quantity in 100 parts of dried cerebral substance, making use for this purpose of the previous determination of the per-centage of solids. The following method was recommended to me by Dr. Stevenson Macadam, of Edinburgh. The weighed brain substance was drenched with lime water, evaporated to dryness, and charred in a crucible. The charred mass digested with heat in diluted hydrochloric acid, filtered, and ammonia added, which precipitated alumina, iron, and phosphoric acid. The precipitate dissolved in a little hydrochloric acid ; a solution of tartaric acid added; rendered alkaline by ammonia; and a stream of sulphuretted hydrogen passed through. Heated very gently, filtered, and evaporated to small bulk. A solution of sul¬ phate of magnesia and ammonia added, which precipitated the phos¬ phorus as phosphate of magnesia and ammonia. The precipitate was then washed with water containing ammonia, dried, burned, and weighed, the ash of the filter being deducted, and the phosphorus determined in the form of phosphate of magnesia. In the carrying out of the foregoing processes all the little chemi-