The Action of Medicines in the System. Frederick William Headland
We find in this division some reference made to the local tendencies of medicines. Evacuants are classed as Stimulants which tend to act locally on the glands. In the arrangement of Dr. A. T. Thomson, founded upon this one, still further reference is made to the local tendencies of different medicines. Dr. Paris also has adopted this arrangement, but in a very much improved form. Both Dr. Thomson and Dr. Paris take exception to the inclusion of Sedatives (under the head of Narcotics) among general Stimulants. This is the great fault of Dr. Murray's classification. The idea, as he states, was taken from Brown. It is considered that both Stimulants and Narcotics act alike; that is, that they both produce a primary stimulation followed by a secondary depression; only that, in the case of Narcotics (under which head all Sedatives are included) the stimulation is very brief, and rapidly passes away, to be followed by a great depression. Now, even if this were true, the most prominent action would be the depressing effect, and it is on the most prominent action that denominations such as these are usually based. But it is well urged by Dr. Thomson that in the case of true sedatives there is no stimulant action whatever; and it is manifestly unreasonable to suppose that the depressing effect follows as a consequence on the primary stimulation, when the latter is so inconspicuous. At any rate such an arrangement as that of Dr. Murray can be of little practical utility in its original form. A man would be considered to be indulging in the wildest and most dangerous fancies who would run through the catalogue of Narcotics when he desired to produce a general stimulant effect. To this system it might further be objected, that Alteratives are again entirely omitted; and that the class of Mechanical agents would seem to belong to the division of Irritants, included among Local Stimulants. Dr. Murray classes Refrigerants among Chemical remedies, for which, when I come to speak of Acids, I hope to show that there are good reasons.
II. Opinions concerning the Local Tendency of Medicines, and Classifications founded upon this.
Here another step is made in the explanation of the action of medicines. They are said to have particular tendencies towards certain parts of the body, over which parts they exert a peculiar and special influence. It is thought that we shall make an advance in our knowledge of the subject, if we can discover what these tendencies are. An arrangement of medicines may be made accordingly. It is certainly more scientific than a merely empirical arrangement; and it will be so far of use that it will enable us, when we wish to make an impression on a certain organ or set of organs, to select those medicines which especially influence it or them. There is no doubt whatever of the existence of these local tendencies. There is no doubt that some medicines, such as Iodine, Bromine, Mercury, and Iron, tend especially to affect the blood and the blood-making organs, as the liver and spleen, rather than to act on the nervous or glandular systems. That some tend particularly towards the nerves, and prefer individually different parts of the nervous system, as Opium acts on the brain, Aconite on the superficial sensory nerves, Digitalis on the organic nerves of the heart, and Stramonium on those of the lungs. Again, it is evident that some medicines tend to act on the organs of secretion; and of these, particular sets select particular glands, as Diuretics the kidneys, Diaphoretics the glands of the skin, and Purgatives those of the bowels. There may be disagreements on minor points, but there can be no dispute as to the fact of the existence of these local partialities.[7]
But, though such statements are admitted to be correct in theory, it remains still to be considered whether they form a fitting basis for a classification of medicines. Now it will be observed that no theory of action enters into such an arrangement, but merely the tendency of the action of each medicine is considered; and as each medicine has naturally many distinct tendencies, it comes therefore under many different heads. But the chief practical use of a classification seems to be, that we may quickly learn from it the general action or effect of a medicine; so that, if it is stated to have many different tendencies, and is ranged under no one particular head, we can gain from this no very distinct practical information respecting it. In an arrangement of the kind that we have last examined, the most important result is the chief point considered. Thus it is rendered useful. And in one of the third kind, where the mode of operation is the great thing taken into account, as each remedy has only one primary operation, and according to this is classified, we gain from its designation some useful information respecting it. It may sometimes come under another head in its secondary operation, but only according to the primary should it be classed, the other term being supplementary. The designations founded on local tendency are further of an indefinite character, because they do not denote the kind of action exerted.
Of such a kind is the classification adopted by Dr. A. T. Thomson, founded on that of Dr. Murray. He divides what he calls Vital remedies into one division that acts on the nervous system, a second that affects the secerning system, and a third that influences the muscular and sanguiferous systems. This is certainly a step in the right direction. Nerve-medicines seem to have no relation to those that act on the glands, though connected with them as Stimulants by Dr. Murray. They are thus separated. Tonics are also separated from Stimulants, and included with those which act on the muscular and sanguiferous systems. This seems to me to be a correct view of their action. I do not consider that they act primarily on the nerves, but on the blood. Dr. Thomson places Astringents beside them. Though alike in some points, as with regard to their tendency to affect the condition of muscular fibre, yet there appears to be very little agreement in the mode of operation of Tonics and Astringents. There is not altogether much similarity between Quina and Sulphuric acid.
I will now transcribe the chief divisions adopted in the classification of Eberle, which seems to have been the prototype of that one since so ably elaborated by Dr. Pereira.
| Dr. Eberle's Classes. | ||
| A. Medicines acting on the intestinal canal, or its contents. | ||
| B. Medicines acting on the muscular system. | ||
| C. On the uterine system. | ||
| D. On the nervous system. | ||
| E. On the circulating system. | ||
| F. On the organs of secretion. | ||
| G. On the respiratory organs. | ||
The subdivisions are founded on the kind of effect produced. As in Dr. Thomson's arrangement, Tonics and Astringents are said to act on the muscles; but no mention is made here of either of them acting on the blood. While Narcotics are placed among nerve-medicines, Stimulants are classed as acting on the circulating system. They no doubt act on the nerves, and then through them on the vessels; but so also do Narcotics, from which they are separated. If in class E are only included medicines acting on the organic nerves of the heart and arteries, why were they not placed in D, with Nerve-medicines? But if medicines acting on the contents of the vessels are meant, why were not Blood-medicines, or Alteratives, placed here? They are entirely omitted; which seems to be a fault in this system.
Dr. Pereira seems to have adopted a more correct view of both of these cases. He includes Stimulants with Neurotics, and places among "Hæmatics" those medicines which are commonly termed Alteratives. It seems to me that when a medicine acts on the blood, this action ought not to be thrown into the shade, but should rather be placed before all its other operations, as being of more importance than any of them. Dr. Pereira arranges in six classes those medicines which are given internally, having previously made three classes of external or topical agents, with which we are not now concerned. Some of the classes are again divided into large groups, these and the other subdivisions being either based on more particular local tendencies, or on the physiological action of the medicine on the part to which its operation