The direct action of nicotin upon the mammalian heart / by Henry G. Beyer.

  • Beyer, Henry Gustav, 1850-1918.
Date:
[1900]
Catalogue details

Licence: In copyright

Credit: The direct action of nicotin upon the mammalian heart / by Henry G. Beyer. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    tricular pressure-tracings are invariably, and very largely, increased under the influence of nicot. blood; the drug, furthermore, exerts a regulating influence on these tracings and, consequently, on the heart’s action itself. Toward the end of the experiment, the heart- beats grew irregular and feeble; normal and we]l-oxygenated blood being run through for eight consecutive minutes, the heart had almost completely recovered its original vigor. The blood in this experiment had, unobservedly, reached a tem- perature 39° C. and, perfusion being in progress before this some- what elevated temperature was discovered, the heart was working at a rather rapid rate in the beginning. On turning on the nicot. blood of the strength 1 : 10,000, we noticed, in the first place, an increased coronary outflow; then a considerable decrease in the number of pulsations and, lastly, a very remarkable increase in the amplitude of the pressure-tracings. During the last ten seconds of the period marked with an asterisk in experiment, the heart beat at the rate of 312 times per minute. These results occur so uniformly with nicotin, used in certain definite proportions, that they must be looked upon as typical. Almost at the precise mo- ment nicotin. blood reaches the heart, the slowing in the rate commences at once; the slowing gradually gives way to an accel- eration and is accompanied by a steady and continued rise in the amplitude of the pressure-tracings, until both acceleration and amplitude have reached a certain maximum which, in every case, is determined by and proportional to the dose of the poison which acted on the heart at the time. The following Fig. 1 illustrates this. The results also seem to harmonize with those obtained by Trail be1 on curarized, but otherwise intact, animals. Traube found that nicotin caused the pulse and arterial pressure to sink at once to half of what they were in the normal animal, when nicotin was injected, but in about 20 seconds the arterial pressure commenced to rise again, attaining a maximum of about two and a half times its normal amount, the pulse-rate also exceeding its original rapidity. Such well-characterized tracings as are represented in Fig. 1 are, however, obtained only when nicot. blood flows through the heart for the first time during one experiment. The heart but slowly recovers its original state after the first strong dose of nicotin has been administered and, furthermore, seems to acquire an immunity or tolerance for the poison, shown by a diminished reaction on all