Report on the progress of human anatomy and physiology in the year 1843-4 / [Sir James Paget].

  • James Paget
Date:
1845
Catalogue details

Licence: Public Domain Mark

Credit: Report on the progress of human anatomy and physiology in the year 1843-4 / [Sir James Paget]. Source: Wellcome Collection.

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    Fatty Principles. Mulder has also discussed, at some length, the chemical physiology of the fatty matters of both plants and animals. He adopts the opinion of Berzelius and Redtenbacher* * * § that the basis of neutral fats is an oxyde of a radical, which they name Lipvle, and of which the formula is C. 3, H. 4, that of the oxyde being C. 3, H. 4, O. With stearic, margaric, and elaic acids, this forms stearine, margarine, and elaine : and glycerine is not present (as such) in the fats, but is formed in their saponification by the union of two equivalents of the oxyde of lipyle, with three equivalents of water. After suggesting the modes in which the several kinds of fat may be trans¬ formed in their passage from plants to animals, and from the body of one animal to another, he considers whether the neutral fats taken as food are conveyed, un¬ altered, into the tissues in which they are deposited, or are saponified, and again reduced into neutral fats by being made to combine with lipyl-oxyde in the body. He supposes they are saponified by the alkali of the bile and chyle; and that glycerine is, at the same time, formed, and carried with them into the blood. The question, in this case is, how is the neutral fat reproduced ? for glycerine will not unite again with the fat-acids to form neutral fats. He supposes that the change is effected by the union of the fat-acids with nascent lipyl-oxyde, and that this is produced in such circumstances as, if more oxygen were present, might give rise to the formation of lactic acid. For when lactic acid is sublimed, a white substance is obtained which has the composition of a binoxyde of lipyl (C. 3, H. 4, O. 2), and of which two equivalents, when it is in contact with water, absorb one equivalent of water, and form lactic acid. And, for explanation of the way in which these changes may be brought about, he refers to the researches of Lehmann}; on the influence of mixtures of fat and albumen in inducing che¬ mical changes in other principles.§ Spontaneous decomposition. Dr. Helmholt,z|| has published some interesting experiments for the determination of the conflicting views respecting the nature of the so-called spontaneous decomposition of dead organic substances. The cjuestion has, for some time, been, whether these are due to the development of microscopic organisms, to which the substances decomposed serve as nutriment, and the secretions of which are the products of the decomposition; or whether the process is one of mere chemistry. In the first place the author confirms the fact already known (but which Liebig tried to explain away) that these decompositions do not take place in substances which have been heated to the boiling point, and which are only supplied with air that has been exposed to a red heat. He found that azotized organic sub¬ stances, derived from the animal proteine- and gelatine-compounds, remained un¬ altered for eight weeks in summer, though freely supplied with air, provided that air had all passed through a red-hot glass tube before coming to them. They consumed the oxygen : but no process of fermentation or decomposition could be detected: yet it soon commenced, with the attendant development of infusoria, when only a small quantity of air which had not been heated was introduced. With other spontaneously-decomposing azotized compounds, these peculiarities are not observed. Hydrocyanic acid and urea decompose as rapidly at the boiling heat and in closed vessels, as they do when exposed to the air. Moreover, when urea decomposes in closed and heated vessels in which it is mixed with other organic substances, neither fermentation nor putrefaction is excited in them by its decomposition. Again, organic substances do not ferment or putrefy when no oxygen is sup¬ plied to them except such as has been immediately derived from water decomposed by electricity. So that it appears that neither oxydation, nor the spontaneous decomposition (resembling putrefaction) of urea, nor the chemical movement pro- * Annalen der Chemie und Pharmacie, August 1843. t The formulae given by Mulder are here adopted, in which water is considered as H. 2, O. | In Simon’s Beit, zur Phys. und Path. Chemie, Bd. i, p. 73 § Physiol. Scheikunde, p. 262-82. || Muller’s Archiv,! 843, Heft v.