It is a mixture of ether (1), rectified spirit (2). Test. - Specific gravity, 0.809. Dose. - 30 to 90 min. Preparation. b.p. Tinctura Lobelia aetherea. Uses

Spirit of ether is used as a carminative and stimulant. It is useful in lessening the pain in the passage of biliary or urinary calculi.

Action of Ether. - When applied to the skin ether evaporates very readily, and causes intense cold. The application of ether to the surface will freeze it completely, and render it perfectly insensitive to pain. If the freezing be continued for too long a time, the frozen part may be killed, and separate as a slough. In the mouth, ether acts as a powerful stimulant to the salivary secretion. In the stomach it increases the secretion of gastric juice, stimulates the movements of the organ, expels flatulence, and probably tends to increase the co-ordination of the movements of the stomach and intestine, so that it diminishes spasm and relieves pain. When absorbed into the circulation from the intestine, or, still more markedly, when absorbed from the lungs after an inhalation, it first stimulates the circulation, and, after a very brief, and perhaps hardly perceptible, period of stimulation of the nerve-centres, it depresses their powers in succession. First of all, it affects the cerebral hemispheres, causing delirium and unconsciousness; next, the grey matter of the spinal cord; next the white matter of the spinal cord, and lastly, the cardiac and vaso-motor centres in the medulla oblongata. It does not appear to destroy the irritability of the muscles in animals poisoned by it; but muscles exposed to its vapour soon lose their contractility, and fall into a condition of rigor mortis. Nerves, also, which are exposed to its vapour, lose their irritability, so that when attempted to be irritated they no longer respond, the irritability of the sensory fibres apparently disappearing before that of the motor fibres. When the vapour is applied only for a short time, they may regain their irritability, but if its application be continued too long, the irritability is permanently destroyed. There is no marked alteration in the blood of animals poisoned by ether, but when mixed in small quantity with blood outside the body, it appears to form a compound with the haemoglobin, and to lessen its oxidising power. If mixed with the blood in large quantity, it destroys the blood-corpuscles, probably by dissolving the protagon which forms an essential constituent of them.

The heart is very much less easily paralysed by ether than by chloroform. If two rabbits are thoroughly narcotised by ether and chloroform vapour respectively, and the thorax opened, and artificial respiration kept up with air containing these vapours, the heart of one can be readily stopped by increasing the proportion of chloroform vapour in the air blown in, whereas the heart of the other is only arrested when the proportion of ether vapour becomes exceedingly large. It is this peculiarity of ether which gives it the advantage over chloroform, and renders death from syncope during operations less probable when ether is employed as an anaesthetic.

Another difference between ether and chloroform, which renders the former much safer as an anaesthetic, is that the vasomotor centre appears, like the heart, to be very much less readily affected by ether than by chloroform, so that irritation of a sensory nerve continues for a longer time to raise the blood-pressure when ether is employed as an anaesthetic. The disadvantages of ether are that it is less agreeable to take, and that its odour hangs unpleasantly about the patient for a much longer time than is the case with chloroform. It causes greater irritation of the air-passages, and may produce a catarrhal condition. It has to be administered in a more concentrated form than chloroform, and thus is not so convenient as the latter when operations on the face and mouth are necessary. It is frequently administered along with nitrous oxide, the nitrous oxide being first given alone until the patient is sufficiently under its influence not to notice the taste or smell of the ether. Nitrous oxide loaded with ether vapour is then given, and as soon as complete insensibility is induced air is mixed with ether vapour, the anaesthesia being maintained by regulating the proportion of vapour according to the condition of the patient. The administration of ether is inadmissible in operations on the mouth and face if the thermo-cautery has to be used.