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"On the modus operandi of narcotico-irritants"

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(14 December 1853)Minutes taken at a meeting of the Physiological Society, a sub-set of the Medical Society of London. Appeared in Lancet 2 (17 December 1853): 586.

PDF courtesy of Elsevier, via the Health Sciences Center Library, Emory University.

Megan Anderson and Cori Heacock made the following transcription:

Dr. Snow read a paper

"On the Modus Operandi of Nartico-irritants."

He said that all narcotics were more or less irritants, causing redness and heat in most cases when applied to the skin, and general excitement when absorbed into the blood. It was the opinion of many physiologists that these agents acted as stimulants, and produced their narcotic effects by exhausting the excitability; but this view was untenable--firstly, because the stimulant effects were often absent altogether, and, when present, they bore no relation to the amount of stupor which might follow; secondly, because excitement often appeared again in the progress of recovery when the insensibility went off; and lastly, because, in the use of volatile narcotics, coma could be kept up or allowed to subside at pleasure, by merely keeping up or leaving off the inhalation, which proved also that the excitability was merely suspended and not exhausted. The connexion between the irritant and the narcotic effects of medicines was of a very close nature, although it was not one of cause and effect. He considered that both the irritation and the narcotism were caused by one power in the agent applied--viz., the power of diminishing oxidation in the living body. A number of reasons were given to show that narcotics have the power of diminishing and preventing the process of oxidation, on which sensibility, muscular irritability, and other animal functions depend. The following are some of the reasons:--The amount of carbonic acid gas produced in respiration had been found to be diminished by certain narcotics, as alcohol, ether, and chloroform. The colour of the venous blood was lighter than usual in patients under the influence of the two latter agents, showing a diminution in the changes which take place at the systemic capillaries. When animals were killed in the space of about five minutes by narcotic vapours, the chief symptoms and phenomena were the same, and occurred in the same order, as in asphyxia by the privation of air. The greater number of narcotics had the effect of preventing combustion, putrefaction, and other forms of oxidation out of the body, their power as antiseptics, &c., bearing a direct relation to their power as narcotics, when they resembled each other in their chemical constitution. Whilst the diminution of oxidation in the system produced narcotism directly, it indirectly caused irritation by inducing congestion in the capillaries and small arteries, where sufficient vascularity existed. Dr. Alison, the late Dr. John Reid, and others, had shown, by facts which he enumerated, that the circulation through the capillaries was assisted by the various changes of composition &c. taking place in the neighbourhood of these vessels, the chief of which consisted in a process of oxidation. When this process was diminished, the flow of blood through the capillaries was impeded, and these vessels became congested together with the smaller arteries, causing the redness and other phenomena of irritation. It was in the most vascular organs and the best nourished persons that irritation and excitement were most frequent. Microscopic observations had shown that the circulation through the capillary blood vessels was impeded or stopped by the action of opium, carbonic acid gas, and some other narcotics. Narcotico-irritants did not increase either the mental or bodily powers of persons in perfect health, in whatever doses they might be administered; but a small quantity of wine or opium often gave temporary energy to those who were in a state of debility. In such persons what blood they had loitered chiefly in the large veins, and a slight obstruction to the capillary circulation, caused it to accumulate a little in the arteries, and the heart was called into increased action to overcome the resistance. Under such circumstances, the better supply of blood to the various organs more than compensated for the narcotic action of the agent employed. From the constant presence of certain narcotico-irritants in the blood for a long period, in Bright's disease of the kidneys, the left ventricle of the heart often became hypertrophied by its efforts to overcome the resistance to the circulation through the capillaries. It had been lately stated that the poison which caused coma and convulsions in this disease was carbonate of ammonia, which arose from the decomposition of urea in the blood, and some experiments he had performed on gold fishes, confirmed this view to a certain extent, as they showed that carbonate of ammonia was a powerful poison, and caused convulsions, whilst urea was hardly poisonous at all.

A discussion ensued, in which Drs. Sibson, Crisp, and Chowne, and Messrs. Richardson and Headland, took part. Dr. Snow replied, and the Society adjourned.

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