Page:Popular Science Monthly Volume 20.djvu/535

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519
PROBLEMS OF PHYSIOLOGICAL CHEMISTRY.

must confess we have no answer, save in exceptional cases. Wherever matter is found definitely arranged, it is also accompanied by effects dependent upon the arrangement; platinum, zinc, and sulphuric acid, when connected in a proper manner, form a galvanic element and give rise to a galvanic current. Similar relations exist in the animal body; here we also find the constituents in a definite arrangement which we term organization, and by means of which the body has control over such peculiar conditions that we can not, or at best only in rare cases, imitate them in the laboratory, and produce the same reactions as are produced by the body. Although we have been taught, by the celebrated discovery of the artificial production of urea by Wöhler, that the compounds occurring in the organism may also be produced out of the body, this and similar experiments have given no explanation of the manner in which the reaction takes place in the organism. Neither have those experiments been explained in which, after the introduction of certain substances into the body, new compounds, not ordinarily present, are found in the excretions. These investigations have, however, considerably increased our knowledge, by showing beyond a doubt that intermediate products are formed in the body, which are generally directly decomposed, and therefore withdrawn from observation, but which can be fixed by the introduction of foreign material, and so protected from further decomposition. How they are produced or fixed is not explained by these experiments; even if we assume, for instance, that the two components unite, with the elimination of the elements of water, we have not the slightest idea how it is effected. Numerous experiments, in which the amount of substances taken up and excreted by the organism were determined, have given valuable results, but not in regard to the reactions taking place in the body. The chemistry of the living body shows the peculiarity that all reactions take place at the temperature of the body, which is quite low, without the intervention of strong reagents in the ordinary sense. If we wish to produce similar reactions outside of the organism, we generally employ a high temperature and substances which would destroy the organism itself. For instance, to prepare hippuric acid from benzoic acid and glycocol, in the laboratory, it is necessary to heat both for some time to 160°, while in the body it is only necessary to dissolve them in blood, and pass the solution through a kidney, when a combination is effected. A problem is here presented, the solution of which is of the greatest importance to physiological chemistry, and which must, therefore, be attempted with all perseverance. It is no longer sufficient to show that certain substances are changed in the animal body, and give rise to the formation of others, nor does it suffice to make the synthesis which the cell produces, by any means whatever, but we must endeavor to work under similar conditions and with the same means as the body itself. We must make our experiments at the temperature of the body, we must employ no reagents