On the immediate principles of human excrements in the healthy state / by William Marcet ; communicated by H. Bence Jones.

  • Marcet, W. (William), 1828-1900.
Date:
1857
Catalogue details

Licence: Public Domain Mark

Credit: On the immediate principles of human excrements in the healthy state / by William Marcet ; communicated by H. Bence Jones. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    substance insoluble in boiling alcohol and remaining on the filter was now submitted to examination; the original alcoholic extract having filtered nearly quite clear through the calico, it was evident that this deposit could consist but in small quantity of insoluble substances, which might have found their way through the meshes of the cloth. The deposit, removed from the filter into a capsule, was boiled with a solution of caustic potash, Avhen the greatest part of it dissolved; an attempt to filter the fluid having failed, I decomposed the alkaline solution with hydrochloric acid, which induced the formation of a precipitate. The precipitate, collected on a filter, was washed with water until the washings ceased to exhibit an acid reaction and induce a cloudiness in a solution of nitrate of silver. Boiling alcohol and ether dissolved the substance on the filter, it cry- stallized on cooling from its solution in alcohol, and by spontaneous evaporation from its solution in ether; by means of repeated crystallizations in a mixture of alcohol and ether, the substance in question was obtained perfectly colourless and pure. When heated on a platina spatula, it fused and then burnt with a flame; a carbonaceous residue was left, which, on the further application of heat, disappeared completely, leaving no ashes on the spatula. When viewed with, the microscope, the crystals had the pecuHar stellate structure of margaric acid; the substance, when fused and allowed to cool, assumed a crystallized nature; it was found to fuse at 60° Centigrade. The above characters are those of margaiic add*, so that this fatty acid is constantly present in healthy human evacuations f. It was now of much importance to ascertain in which form the margaric acid found in the above circumstances existed as a constituent of human fseces, or in other words, to determine the Immediate Principle containing the fatty acid in question; but pre- vious to entering on this subject, I beg to relate an experiment instituted for the pur- pose of detecting the best method to be employed to prepare the alcoholic extract of excrements. It was noticed that the quantity of the deposit yielded by the extract, on cooling, varied according to the manipulations adopted to prepare the solution; conse- quently a healthy and fresh evacuation was triturated in a mortar, in order that every part of it should be equally moistened, and the mass was di\ided into three quantities, weighing each 60 grammes. Each portion was boiled four times successively with two ounces of alcohol; the first part being treated with alcohol in an open tin capsule and strained through a clean laboratory towel, the second being boiled in a long-necked flask and strained through the same towel, and the third being treated in a similar flask and strained through muslin folded in two. The fluid passed very freely through the muslin, and there appeared to be a greater deposit on cooling in the alcoholic extract of the third portion than in that of the two others; about two hours afterwards the alcoholic extracts were filtered separately through filtering-paper, and a clear dark-colom'ed solu- * Notwithstanding the fusing-point and crystaUine structure of this fatty acid, it might have been mixed with a small proportion of stearic acid and traces of oleic acid. Stearic and margaric acid have the same chemical properties. t I had shown in my previous communication that margaric acid was occasionally present in fseces. I