An amusing illustration of the reverence which this doctrine of the temperatures inspired is furnished by Sprengel in the second volume of his History of Medicine. Dealing with the Arab period, he tells us that Jacob-Ebn-Izhak-Alkhendi, one of the most celebrated authors of his nation, who lived in the ninth century, and cultivated mathematics, philosophy, and astrology as well as medicine, wrote a book on the subject before us, extending Galen’s theory to compound medicines, explaining their action in accordance with the principles of harmony in music. The degrees he explains progress in geometric ratio, so that the fourth degree counts as 16 compared with unity. He sets out his proposition thus: _x_ = _b_^{_n_-1}_a_; _a_ being the first, _b_ the last, _x_ the exponent, and _n_ the number of the terms. Sprengel has pity on those of us who are not familiar with mathematical manipulations, and gives an example to make the formula clear. Medicament. Weight. Hot. Cold. Humid. Dry. Cardamoms ʒi 1 ½ ½ 1 Sugar ʒii 2 1 1 2 Indigo ʒi ½ 1 ½ 1 Myrobalans ʒii 1 2 1 2 --- ----- ----- --- --- ʒvi 4½ 4½ 3 6 This preparation therefore forms a mixture exactly balanced in hot and cold properties, but twice as dry as it is humid; the mixture is therefore dry in the first degree. If the total had shown twelve of the dry to three of the humid qualities, it would have been dry in the second degree. When it is remembered that in addition to these calculations the physician had to realise that drugs adapted for one part of the body might be of no use for another, it will be perceived that the art of prescribing was a serious business under the sway of the old dogmas. THE ROSICRUCIANS.