This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Chloroform, in its local action, is first irritant and afterwards sedative; in its general influence is powerfully sedative, primarily to the nervous system, and secondarily to the respiration and circulation. When it first became known as a medicine, I was disposed, with others, to consider it a stimulant of the same class as ether, alcohol, and opium; but I soon found that it was impossible to reconcile some of its most obvious effects with this view of its powers, and, having made a more particular investigation into its operation, became convinced that it was directly and essentially sedative to the nervous system generally, and especially to the brain. in a number of patients, to whom I gave it internally, in doses of from thirty to seventy drops, I could detect no evidence of increase in the cerebral functions, or in the action of the heart, but found it moderately sedative to both. A young medical gentleman, who took a fluidrachm of it, assured me that he experienced no mental excitement, though a pleasing calmness was induced, with some cerebral confusion, and a feeling of drowsiness. The pulse was at no time in the least accelerated, but soon became somewhat less frequent; nor was there any heat of skin, or hurry of respiration. Dr. Henry Hartshorne, at the time resident physician in the Pennsylvania Hospital, made various trials with it upon himself, and in the wards under my care, with the same results. "From seventy-five drops of it there was a diminution of consciousness and sensorial capacity; sight, hearing, and touch became less impressible; and positive drowsiness was produced. There was no feel-ing of exhilaration or disorder; and the pulse, so far from being accelerated, was reduced two beats in the minute." (Am. Journ. of Med. Sci., Oct. 1848, p. 353.) in relation to the effects of doses larger than a fluidrachm, M. Aran has recorded a case in which a quantity, supposed to be from eight to ten drachms, was swallowed in mistake by a man. There was at first a burning sensation produced, with ineffectual efforts to vomit; in a few minutes afterwards he was found with his eyes glistening, his features animated, singing and talking incoherently, and unable to recognize those about him. There were some convulsive movements; the skin was insensible to painful impressions; sight was lost; and the pulse was between seventy and eighty. in the course of twenty or thirty minutes sleep ensued, which became very deep, and was attended with insensibility of the surface, and complete relaxation; the respiration and circulation remaining normal. The sleep continued several hours. Next in consequence of its local irritant property, chloroform not unfre-quently occasions nausea and vomiting, especially when not thoroughly suspended, and equally distributed in the vehicle in which it is given. its weight and insolubility probably produce this effect, causing it to fall against the surface of the stomach, and thus to act in an undiluted state upon the mucous membrane. By proper administration, this effect may, to a considerable extent, be avoided. Nevertheless, in my experience, it is the strongest objection to the internal use of the medicine, which, so far as its influence on the system is concerned, may, I believe, be given with perfect safety in any moderate dose.
When applied to any sentient part, chloroform produces at first a painful burning sensation, with more or less rubefaction, and sometimes vesication. in a short time the irritation ceases, and is followed by a more or less entire loss of sensibility in the part, with relief to any existing pain, which is often surprisingly sudden and complete. The irritant impression is of course stronger upon the mucous membranes, or an abraded surface, than on the sound skin, in which, however, when the chloroform is undiluted, the smarting and burning are often severe. Some degree of the same effect is produced by the vapour, similarly applied; though much less considerable. Diluted to a much less extent than as it must exist in the circulation, the medicine quite loses this irritant property, and becomes perfectly bland; so that the possession of the property by no means implies that the chloroform, when absorbed, will in the slightest degree excite the parts with which it is brought into contact. The local anaesthetic power of chloroform was noticed by MM. Flourens, Serre, and Longet, who, in their experiments upon animals, observed that, when applied to the extreme nerves uncovered, it rendered them completely insensible. But credit is more particularly due to Dr. Nunneley, for having drawn attention to this property, not only in chloroform, but in other agents also, and for showing that advantage might be taken of it for practical purposes. He proved that the insensibility was not confined to the precise locality of the application, but extended also a considerable distance along the nervous trunk.
Effects from inhalation. When the vapour of chloroform is inhaled, it first produces an irritant impression on the mucous membrane of the air-passages, which, however, is inconsiderable, and scarcely more than momentary, and is soon followed by a local torpor and relaxation, dependent probably upon the direct contact of the agent. But all merely local effect is very speedily absorbed in the powerful impression made on the system. The inhalation may be effected by simply holding the chloroform in the vicinity of the mouth and nostrils. The vapour enters with the air inspired. When but a small quantity of the liquid is employed, as from twenty to thirty minims, its effect begins to be felt in the head within a few seconds. The brain becomes somewhat confused, abnormal sounds are heard, sight is disordered, a vague sense of pleasure is experienced, hallucinations, generally agreeable, and sometimes apparently ludicrous, are produced, and a loss of consciousness, more or less complete, takes place, generally with quiet sleep, but occasionally with dreamy, incoherent speech, or laughter, and very rarely turbulence. Consciousness returns in five or six minutes, with either no recollection, or a confused one of what had passed. If the quantity used is somewhat larger, say one or two fluidrachms, the effect is more rapid and powerful. Feelings of an agreeable character are soon followed by diminished sensibility, general numbness, mental obtuseness, drowsiness, complete loss of consciousness, and profound sleep. The eyelids droop; the pupils are dilated, though contractile, and roll upwards; the breathing is slow, often stertorous, and sometimes with frothing at the mouth; sensibility and the power of movement are quite lost; and the muscles are in general universally relaxed, though in rare instances slight convulsive twitchings of the face and limbs are observable. The pulse is sometimes momentarily quickened at first, though enfeebled; more frequently it is diminished both in frequency and force; and in some instances it becomes extremely weak. In general, however, it is not very materially affected, unless the application be continued longer than necessary to induce sleep. From the state of deep stupor or coma, the patient usually passes, for a short time, into a soft sleep, or dreamy drowsiness before fully awaking; but not unfrequently there is an immediate return to complete consciousness and power of motion. There is generally no recollection of what has passed. None of the secondary headache, lassitude, sickness, and loss of appetite are experienced, which so often follow the action of the cerebral stimulants. The case is related of a person who inhaled as much as a pound, at intervals, in the course of five or six days, and yet, on each occasion, after recovery from its immediate effects, felt not the slightest uneasiness. (Med. Times and Gaz., Nov. 1857, p. 533.) This is one of the strongest proofs that its action is essentially sedative; for the operation of stimulants is almost invariably followed by evidences of greater or less depression.*