In what way is the action of drugs to be discovered? : an essay / by William Sharp, M.D.

  • Sharp, William, 1805-1896.
Date:
1873
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Licence: Public Domain Mark

Credit: In what way is the action of drugs to be discovered? : an essay / by William Sharp, M.D. 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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    boundaries, as is seen in the manufactures of glass* and of steel.f Heat, indeed, often excites the action of chemical affi- nity, or brings it into play; but in the instances given, it produces compounds independent of the controlling power of chemical affinity, as that force is at present understood. The components are not combined in definite proportions, and yet the properties of the compounds greatly differ from those of the component parts. Life has a still greater power in limiting the action of chemical affinity, which, however, it does not destroy nor supersede. As regards the action of drugs, chemical analysis helps us when it can show the presence of the drug in the organ in which its action has taken place; but chemical affinity renders us no assistance in the investigation of the action. A final remark on chemistry. The forces in nature with which we are best acquainted are those of attraction and repulsion. Among attracting forces are gravitation, which acts between all particles of matter at sensible (sometimes at inconceivably great) dis- tances ; cohesion, which acts between similar particles of matter at insensible distances ; and chemical affinity, which acts between dissimilar particles of matter at insensible distances. Chemistry is the branch of science which occupies itself with the phenomena belonging to this last kind of attraction. It is an experimental science. The results of its experiments are surprising and beautiful, and have been made eminently useful to man. When occu- ® Chemists speak of glass as a true chemical and therefore a definite combination, and suppose flint-glass to be a silicate of potash and oxide of lead ; crown-glass a silicate of soda and lime; and so of other kinds of glass. But this has not been established by experiment. Many years ago, having at the time free access to, and ready use of some large glass furnaces, I availed myself of the opportunity to try a series of experiments, in order to test this point. The ingredients ■were carefully combined in the proportions of their chemical equiva- lents, coming as near to the empirical proportions used by the manu- facturers as calculation permitted. My glass was made at the same time, and in the same furnace as the Mother. But the glass whose ingredients were mixed by rule of thumb far surpassed in all its properties that mixed by rule of equivalents. t Steel, the properties of which, it is well known, differ much from those of iron, is a compound of iron with a variable percentage of carbon.