2. Mode Of Operation

Enough has been said already of the local action of chloroform. in relation to its operation on the system, few, I presume, doubt that it produces its effects through absorption into the blood.* The odour of the breath of those who have taken it largely by the stomach, and the fact that it has been detected after death in the blood and different parts of the body, are sufficient proofs of absorption. it has been supposed by some that its primary influence is on the blood, which it is thought to change chemically, rendering it of a darker colour, and unfit for the support of the vital phenomena. But in opposition to this notion is the great rapidity with which its effects appear and disappear; and, besides, it is asserted, as the result of experiment, that it does not blacken, but on the contrary reddens the blood, when added to it out of the body. (See Am. Journ. of Med. Sci., N. S., xxvi. 188.) When the blood is darkened, as it sometimes is under the poisonous action of chloroform, the result must be ascribed to the want of change in the lungs, consequent on the defect of respiration. The blood in all probability merely serves as a vehicle for the medicine, by which it is brought into contact with the tissues upon which it operates. That the nervous centres are the parts primarily affected seems to me to be a necessary inference from the symptoms, which are at first exclusively nervous; for the excitement of the pulse, sometimes observed when it is administered by inhalation, is by no means constant, is at most very brief and fugitive, disappearing as soon as the true influence of the medicine is felt, and is in all probability quite as much the result of the agitations of the occasion as of the action of chloroform. it may possibly also proceed from the sympathy of the circulation with the primary excitant impression, made by its vapour on the fauces, and bronchial mucous membrane.

* The idea has been advanced that the main source of danger, in the inhalation of chloroform, is not its direct influence on the cerebral centres, but a local anaesthesia of the lungs, produced by the contact of the vapour with the intimate structure of these organs, through its admission into the minute bronchial tubes and the air-cells, and its entrance by endosmose into the capillaries. There can be no doubt that a local paralysis of this kind would give rise to a suspension of respiration, and death from asphyxia. This idea was put forth by Dr. T. L. Maddin, of Nashville, Tenn., in a paper read before the Tennessee State Medical Society, in April, 1858. (Nashv. Month. Record, etc., i. 29.) in a series of papers, by Dr. Faure, of Paris on the subject of asphyxia by chloroform, contained in the Archives Generates, and commencing in the number for June, 1858, the same idea of the local action of chloroform in the lungs is maintained; but the result is ascribed by Dr. Faure, not to an anaesthetic influence upon the nerves of the tissue, but to the influence of the poison upon the blood in the pulmonary capillaries, which is supposed to be coagulated, or at least so thickened and altered as to be unable to circulate. it is asserted by Dr. Faure, as the result of his experiments, that chloroform cannot be absorbed; and that its action is always local. (Arch. Gén., 5e sér., xi. 642.) But this is assuredly a mistake; for we have had abundant evidence of its absorption, in the cases in which it has been taken in poisonous doses into the stomach, in all of which the breath smells strongly of the narcotic. Though it is certainly possible that asphyxia might result from the local ana3Sthetic influence of chloroform on the pulmonary tissue; yet, as we have the same phenomena, to a considerable extent, resulting from its exhibition by the stomach and lungs, though they are more rapidly produced through the latter, it is most probable that they proceed in both from the same source; from the absorption, namely, of the poison, and its direct action on the cerebral centres. Besides, death has sometimes taken place so rapidly, and from a quantity so small, that the effect could scarcely have resulted from a local anaesthesia of the lungs; and, in some instances, the fatal action seems to be directly on the heart, probably through its nerve centres, producing syncope, and not on the respiratory function, causing asphyxia. (Note to the second edition.)

Admitting its primary operation on the nervous centres, we are next to examine which of them are affected. The loss of sensibility, the quick suspension of consciousness, and the relaxation of the voluntary muscles, point incontestably to the cerebral centres, those of sensation, intellect, emotion, and will - in other words, the nervous centres of animal life - as the primary seat of impression. But, as sensibility to pain is abolished before consciousness, it follows that the centres of sensation are affected previously to those of thought and volition. Though the cerebral symptoms are certainly first observable, yet they are soon accompanied with those of respiratory and circulatory disorder, which increase as the former deepen; so that, when coma is fully established, the respiration has become slow and often stertorous, and the pulse also lowered in frequency and force, though in general not considerably so. it is evident that, by this time, the respiratory centre in the medulla oblongata is under the influence of the medicine; while the heart is probably depressed secondarily to the respiration. Lastly, under a longer continuance of the agent, the reflex centres in the spinal marrow, and possibly those of the ganglionic system suffer; and hence the occasional relaxation of the sphincters, the want of tonicity in the muscles, the flabby state of the heart, and the universal debility which supervene, with a still greater depression of the respiration and the pulse. Carried a little further, the medicine becomes a poison, and death from asphyxia takes place, with general venous congestion, but especially of the lungs.