The humours had different characters. The blood was naturally hot and humid, the phlegm cold and humid, the bile hot and dry, and the black bile cold and dry. Alterations of the humours would cause diseased conditions; distempers was the appropriate term. There might be a too abundant provision of one or more of the humours. A plethora of blood would cause drowsiness, difficulty of breathing, fatty degeneration. A plethora of either of the other humours would have the effect of causing corruption of the blood; plethora of bile, for example, would result in a jaundiced condition, bad breath, a bitter taste in the mouth, and other familiar symptoms. Hæmorrhoids, leprosy, and cancer might result from a plethora of the melancholic humour; colds, catarrhs, rheumatisms were occasioned by a superabundance of the phlegm. It must not be supposed that Galen or any other authority pretended that the humours were the sole causes of disease. Ancient pathology was a most complicated structure which cannot be even outlined here. The theory of the humours is only indicated in order to show how these explained the action of drugs. To these were attributed hot, humid, cold, and dry qualities to a larger or less extent. Galen classifies them in four degrees--that is to say, a drug might be hot, humid, cold, or dry in the first, second, third, or fourth degree. Consequently the physician had to estimate first which humour was predominant, and in what degree, and then he had to select the drug which would counteract the disproportionate heat, cold, humidity, or dryness. Of course he had his manuals to guide him. Thus Culpepper tells us that horehound, for example, is “hot in the second degree, and dry in the third”; herb Trinity, or pansies, on the other hand, “are cold and moist, both herbs and flowers”; and so forth. Medicines which applied to the skin would raise a blister, mustard, for example, are hot in the fourth degree; those which provoke sweat abundantly, and thus “cut tough and compacted humours” (Culpepper) are hot in the third degree. Opium was cold in the fourth degree, and therefore should only be given alone to mitigate violent pain. In ordinary cases it is wise to moderate the coldness of the opium by combining something of the first degree of cold or heat with it.