Having very little power, in moderate doses, to depress the action of the heart, it is preferable to chloral hydrate in cardiac diseases and debility. Sleep procured with doses of fifteen to sixty grains is calm and refreshing, and is not followed by any disagreeable consequence. A certain degree of tolerance is gradually established, so that larger doses may become necessary. It has been given in quantities amounting to three drachms; but, if large doses be given before the development of tolerance, the patient will experience headache, uneasiness, nausea, and vomiting, after waking from the sleep thus induced. Another advantage possessed by paraldehyde consists in the absence of the period of excitement produced by chloral before the advent of sleep. It is an hypnotic, without narcotic properties, limiting its effects chiefly to the brain, and leaving the spinal cord in a condition nearly like that of natural sleep. _Ether_, though possessed of the greatest value as an agent for the production of artificial anæsthesia, is rarely used as a mere hypnotic. Diluted with alcohol and ethereal oil, it forms the _Compound Spirit of Ether_, or _Hoffmann’s Anodyne_. In this form it is well adapted for internal administration. It is thus very serviceable in the treatment of those forms of insomnia associated with nervous irritability and hysteria. For the relief of wakefulness dependent upon a languid circulation, with cold feet and flatulence, the anodyne may be given in half-drachm doses well diluted with ice water, and repeated every fifteen minutes till relief is obtained. Nearly all forms of painful or spasmodic disturbance unattended by fever may be thus relieved. For this reason it is particularly useful in the treatment of uterine colic and in sleeplessness after childbirth, when opiates cannot be tolerated, or are contra-indicated on account of their tendency to excite the brain.