The diminution of the cutaneous sensibility, by the application of ice and freezing mixtures, has long been practiced. It was not, however, until Richardson's method by the hand-ball spray apparatus had been proposed, that there had been much use made of local anaesthesia.

This method consists in directing a current of atomized ether against the part to be anaesthetized. The ether employed for this purpose should have a specific gravity not to exceed 0·723. Rhigolene, the lightest liquid known, a product of the fractional distillation of petroleum, is more effective than ether, but great difficulty attends its use, owing to its extreme volatility. When a current of atomized ether or rhigolene is directed against the skin, the rapid evaporation produces an intense degree of cold, in consequence of which the nerves lose their power of transmitting impressions to the sensorium.

A serious drawback to the process of producing local anaesthesia is the unpleasant burning which follows in the part when it recovers from the freezing, and also the great pain which attends the application of ether-spray to certain parts.

Therapy

For small operations, such as extraction of teeth and opening abscesses, the method of local anaesthesia is extremely useful. It has been and can be used with entire success in much larger operations, but it is generally employed for merely minor ones.

The application of ether-spray to the spine is an extremely serviceable remedy in spinal irritation and in chorea. In the latter disease it alone suffices to effect a cure. In neuralgia of superficial nerves, lumbago, muscular rheumatism, etc., the ether-spray affords relief very quickly, which may be permanent.