This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Ether probably operates as a stimulant by a direct influence on the vital susceptibilities of the tissues, without any chemical reaction. One proof of this is the vast amount which may be taken with impunity, after the system has become accustomed to it, by a gradual increase of the dose. The case of a chemist is recorded, who took a pint of ether daily. (Merat and De Lens, iii. 166.) When large quantities have been introduced by inhalation, the observable effects often cease long before the evidence afforded by the breath that a portion still remains in the system. This could scarcely be, if the effect were chemical, whether on the solid tissues, or the blood. The higher carbonization of the blood has been supposed to have something to do with the effects of ether. This, however, is probably a mere respiratory result. That the first stimulant impression on the circulation, respiration, and cerebral functions, may depend on the propagation of the local influence, through the nerves, to the nervous centres of those functions, is not impossible; and the rapidity with which the effect is produced might be advanced as an argument in favour of this view; but experiments have satisfactorily shown, that the round of the circulation is accomplished in time to permit the operation by this route within the actual period; so that the view referred to cannot by any means be considered as demonstrated. The probability is that most of the effects of ether are due to its absorption into the circulation, and direct action upon the nervous centres, the functions of which are first increased by the stimulation, then deranged, and afterwards diminished or temporarily suppressed, under the general law of irritation. I have already referred to the relative degree in which the centres are susceptible, deduced from the period at which they respectively come under its influence. That ether is absorbed, is almost too obvious to require proof. The odour of the breath, which always smells strongly of ether, in whatever way administered, is a sufficient evidence; not to allude to the fact, that its odour has been noticed in the ventricles of the brain, when death has from any cause followed soon after its exhibition. The great difference in the effects of the medicine, as adminis-tered by the stomach and the lungs, is probably owing to its much slower absorption from the former organ. Its powerful direct stimulant action. in the liquid state, upon the stomach, producing an active congestion of the blood-vessels, may be one reason of its relatively slower absorption through this organ than the lungs, when compared with some other volatile medicines, such as hydrocyanic acid.