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 tends. DR. PEREIRA'S CLASSES. CLASS IV. Hæmatica. 1. _Spanæmica._ 2. _Hæmatinica._ CLASS V. Pneumatica. CLASS VI. Neurotica. 1. _Cerebro-spinalia._ 2. _Ganglionica._ CLASS VII. C[oe]liaca. CLASS VIII. Eccritica. CLASS IX. Genetica.