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Medical Times and Gazette
(21 June 1856): 680-81

[Digital copy courtesy of Google.

Mr. Witten's letter was published as "No. 114--Chloroform" in the Notes and Queries section of the journal (14 June 1856): 604. The PDF includes a copy of Witten's letter, as well as Snow's response.]

(To the Editor of the Medical Times and Gazette)

Sir,--I shall feel obliged if you will allow me to state, with respect to the case mentioned by Mr. Witten, and the question he asks in your Journal of to-day, that every patient may inhale the quantity of choloroform [sic] he mentions, vis., 8 or 9 drachms, without being rendered unconscious, provided the inhalation be extended over a sufficiently long time. It is the custom to give it so in certain cases of labour, especially during the first stage. On the other hand, I am satisfied, by long and careful observation, that every patient may be rendered insensible by the vapour of one fluid drachm of this agent, provided it be inhaled continuously and without intermission, and be diluted with not more than fifteen hundred cubic inches of air. I have had to give chloroform to a number of patients on whom large quantities of chloroform had previously been used without effect, and I have not found that any of them required to inhale more than other persons of similar bulk and strength.

Whenever I have met with unusual delay in rendering [a] patient insensible, I have been able to trace it to the circumstance, that the vapour did not enter the lungs in sufficient [680/681] quantity with the inspired air. When the vapour enters the lungs, a large portion of it is necessarily absorbed into the blood; and being in the blood, it cannot help acting on the brain and nerves, according, as I feel assured, to a regular and definite law. But exhalation goes on in the lungs, as well as absorption; and if the inhalation of the vapour is interrupted only by a few seconds, the patient loses part of the chloroform which had previously been absorbed; moreover, if the vapour be too much diluted with air, there comes a point where the exhalation from the blood in the lungs balances the absorption, and no further effect can be produced though a person should inhale for hours. The true reason why Mr. Witten's patient did not become unconscious is, that the quantity of chloroform present in the circulating fluid never at any moment reached twelve minims, and was probably much below that amount.

I am, &c.

John Snow, M.D.

Sackville-street, June 14.

[Mr. Witten's reply was published in the issue appearing 28 June 1856 (page 651). He concluded with the following sentence: "Permit me, through your columns, to thank Dr. Snow for his kind though unsatisfactory answer." The ball now unexpectedly back in his court, Snow wrote another letter, which appeared on 5 July.]

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