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.
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.