Cullen denied their existence; but it is generally admitted that certain substances may, either by invigorating the system generally, or by their local action, stimulate the organs of generation. Dr. O'shaughnessy states that Cannabis is unequivocally aphrodisiac; and Nux Vomica, with its active principle Strychnine, as well as Phosphorus and Cantharides, undoubtedly appear to act as sexual stimulants. Impotence is the only disease which requires their use. Many articles of diet, as oysters, &c. are reputed aphrodisiacs, but on insufficient grounds.

2909. Astringents are agents which cause a contraction of the capillaries, constringe muscular fibre, coagulate albuminous tissues, and solidify the parts to which they are applied. When used externally, to arrest superficial hAemorrhage, they are denominated Styptics. The purposes for which they are employed are thus enumerated by Dr. Pereira - 1, to stop preternatural secretion from mucous surfaces, as in Leucorrha, Gonorrha, and Gleet; 2, to check profuse secretion from ulcerated surfaces; 3, to stop hAemorrhage, as from the uterus and piles; 4, to strengthen and constringe relaxed parts, as in prolapsus; 5, to subdue inflammation of superficial parts, e.g. Nitrate of Silver in Erysipelas. When thus used, they are sometimes called Repellants. The great majority of astringents act chemically, coagulating the albumen of the blood.

. Indications for their Use. 1, Atonic or passive HAemorrhage; 2, non-inflammatory Diarrha; 3, Diabetes; 4, chronic discharges, as Gonorrhoea, Gleet, and Leucorrha; 5, excessive mucous discharges from the lungs, stomach, bladder, and other mucous surfaces, when attended with relaxation of the parts, and atony of the system; 6, ulcers with copious secretion; 7, profuse perspirations of Phthisis, and other diseases.

Contra-indications. 1, Inflammation; 2, Active HAemorrhage, Inflammatory Diarrhoea, and excessive mucous discharges attended by inflammation; 3, rigidity of parts; 4, extensive external injuries. In these cases the local application of astringents will not only fail to arrest the hAemorrhage, but may excite excessive irritability or inflammation of the surrounding tissues. (See Styptics.)