Dr Sansom says of chloroform:—“The cause of its danger is its power of paralysing the cardiac and other motor sources of circulation. This property resides in large and sudden doses of its vapour.” He strongly recommends its dilution by air and alcohols. He further remarks that all anæsthetics modify the endosmotic condition of the blood discs, and contends that they affect the supply of arterial blood by altering the calibre of the channels which convey it. He advocates the substitution of one anæsthetic for another during the inhalation.
Methylene dichloride, introduced by Dr B. W. Richardson, is said to possess the disadvantage of causing considerable depression.
The mode of administering these agents is by causing the patient to inhale their vapour mixed with air.
Sometimes they are poured on to a sponge or a handkerchief, or piece of lint, either of which is then applied to the mouth and nostrils of the patient in such a manner that the air which passes into his lungs is saturated with the vapour. Except in extemporised cases, however, this method is pretty well abandoned, a proper apparatus having supplanted the sponge or handkerchief, &c. Part of the apparatus consists of a graduated bottle containing the anæsthetic, by means of which the operator is enabled to tell how much of this latter is being consumed, and thus to regulate the quantity inhaled.
The first effect that results from the administration of anæsthetics is a form of intoxication, caused by the action of the anæsthetic agent on the cerebral lobes, and as this action extends to the cerebellum, the patient becomes incapable of directing his movements—an effect like that caused by intoxication from alcohol.
In the next stage the spinal cord is attacked, unconsciousness supervenes, and all powers of motion and sensation are lost. The individual is now said to be in a state of anæsthesia; but the heart continues to beat, respiration is not impeded, and the other essential functions of the body go on as usual.
Should, however, the exhibition of the anæsthetic agent be incautiously continued too long, the bodily temperature falls, the movements of respiration and circulation become impaired, the heart ceases its action, and death finally ensues. The introduction of anæsthetics into surgical practice has been of great and invaluable service to the operator. The patient being motionless and free from pain, the surgeon is enabled to perform the operation at his ease, and consequently more efficiently; moreover, in the reduction of dislocations and of hernia, the muscles being flaccid, the obstacle produced by their contraction is removed. M. Velpeau endeavoured to produce local anæsthesia, or insensibility of the part of the body to be operated upon, by means of a freezing mixture composed of ice and salt; this method, however, was found impracticable, and was soon abandoned. Since then local anæsthesia as introduced by Dr Richardson, when had recourse to, is effected by means of a spray of ether directed on the part, the intense cold produced by the rapid evaporation of the ether entirely
depriving the part of sensation. It is said that the pain resulting from the application of this method is a great barrier to its use.
Amongst anæsthetics, nitrous oxide gas occupies an important place, its use, as before stated, being almost wholly confined to operations in dental surgery.[55] As in the case of ether, the American practitioners were the first to employ nitrous oxide as an anæsthetic. Attention was directed to its anæsthetic properties in 1844 by Mr Horace Wells, an American dentist, but little interest seems to have been awakened by his application of it, since it was not until 1863 that Dr Cotton, of New York, drew attention to the subject by performing an operation on a patient under its influence.
[55] The ‘British Medical Journal’ for 1868 states it was used successfully at the Ophthalmic Hospital, Moorfields.