These are medicines which increase the sexual appetite.

Irritation of the nates, either mechanically alone, by flogging, or mechanically and chemically combined, by urtication or flogging with nettles, has been used as an aphrodisiac.1

1 Trousseau et Pidoux, Traite de Therapeutique.

The sexual function requires, however, for its proper performance a healthy state of the body, and good, or at least fair, nutrition; without these mere reflex excitement of the genital centres is likely to prove inefficient for the propagation of the race. Tonics generally, such as iron, are therefore to be regarded as indirect aphrodisiacs.

Strychnine has probably a double action, both increasing the general nutrition and rendering the genital nervous centres, both lumbar and cerebral, more susceptible to the action of stimuli. Its aphrodisiac action is sometimes an objection to its use as a tonic, for both it and nux vomica may cause seminal emissions which more than counterbalance its tonic action and weaken the patient.

Cannabis indica has been regarded as an aphrodisiac, but the trials of it made in this country seem to show that it does not itself at least have any such action, and merely induces a condition of partial delirium in which Easterns may possibly have visions of a sexual nature, and indeed, they try to give a sexual direction to the mental disturbance which the cannabis produces, by mixing with it musk, ambergris, or cantharides.

Catharides act as an aphrodisiac, but their action is probably due to an irritating effect on the mucous membrane of the urethra, and their use in such doses as to have any aphrodisiac action is attended with danger. Blatta orientalis when used as a diuretic may have an aphrodisiac action like cantharides.1

Alcohol appears to excite the cerebral centre and increase the sexual appetite, while it interferes with the proper performance of the generative act.2 This interference may be due to partial paralysis of the lumbar centre or the nervi erigentes; but paralysis of the vaso-motor centre is probably a potent factor, or may indeed be the only cause of the impotency produced by alcohol; for alcohol paralyses the vaso-motor centre to such an extent that it will not react to the stimulus of venous blood, and even suffocation will not raise the blood-pressure.3 Consequently, the rise in blood-pressure which holding the breath will normally produce during coition (p. 447) will not occur when much alcohol has been taken, and the penis, although it may be turgid from dilatation of the vessels, will not acquire the rigidity necessary for the generative act.

1 Buttenwieser, Der practische Arzt, Feb. 1882.

2 Shakespeare, Macbeth, act ii. scene 3.

3 Dogiel, Pfluger's Archiv. vol. viii.