Heart / by John Reid.

Date:
1838
Catalogue details

Licence: Public Domain Mark

Credit: Heart / by John Reid. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    i ing tlie frothy blood from the right side of tlie I heart. It is also necessary to remember tliis ^ circumstance in experimenting upon the length . of time during which the heart remains con- I tractile after death, as the division or non-divi- ■ sion of the large veins at the root of the neck in laying open tlie thorax may considerably modify the results.* For the probable force exerted by the heart, !the share which the heart has in carrying on the 1 circulation, and the.probable quantity of blood I expelled at each contraction, see the article ' ClKCCLATlON. Frequenn/ of the heart's action.—The fre- 1 quency of the heart's action is considerably 1 modilied by age, condition of the other functions I of the body at the time, by mental emotions, and Iby the original constitution of the individual. Its movements are influenced by very slight : muscular exertion, and the extent of this appears I to vary at different times of the day. In the I foetus its movements are rapid, being about 140 in the minute. At birth it is from 130 to 115 to 130; second year 90 to 100; seventh 85 to to 85; middle age 70 to 50 to 65. The heart's 140; at one year 100 to 115 ; third i90; fourteenth 80 ! 75; in very old age m action generally sympathises powerfully with the other organs of the body, and this has always been regarded as a mostimportantand necessary guide in the detection and cure of diseases. It becomes strong and rapid in some cases of inflammation, while in others it becomes rapid and feeble. It becomes quicker after eating and slower during sleep. It is much increased in frequency during bodily exertion. In cases of great general debility it becomes very quick and feeble. It becomes more rapid and weaker during inspiration, slower and stronger during expiration. It is an important fact that when the con- tractility of the heart is much enfeebled by extensive injuries of the central organs of the nervous system or of the other parts of the body, (as when a limb is extensively crushed,) its contractions are not only much weaker, but are also greatly increased in frequency. It is also worthy of remark that such injuries do not pro- duce convulsive movements in this organ. The effect which severe injuries and certain inflam- matory aflTections have in greatly debilitating or even destroying the contractility of the heart is a fact of great practical importance, as it not only explains the cause of the most alarming symptoms in such cases, but also points out the most appropriate remedies to avoid the chief tendency to death. To this cause, for example, we are to attribute the rapid and feeble pulse, in concussion of the brain, in extensive mecha- nical injuries, the shock after operations, exten- * Edinburgh Medical and Surgical Journal, 1836. When I performed these experiments, I was not a aware that I had been anticipated to a certain ex- 1 tent by Mr. Coleman. ( Wilson on the Blood, &c. f p. 131.) It is very possible that the sinuses upon I the inlerior cava and hepatic veins in the seal may, 1; besides answering other purposes, have the clTect of preventing this mechanical distension of the r right side of the heart. sive burns, peritonitis, &c. It is very fortunate that the contractions of the heart become more frequent when its contractility becomes en- feebled. If the heart under these circumstances had required, as we would a priori expect, the presence of a greater quantity of blood to stimulate it to contraction, instead of a smaller quantity, as is actually the case, what would have been the consequence ? It is evident that since the resistance, under ordinary cir- cumstances, which the heart has to overcome in contracting, is, according to a well-known hy- drostatic law, in proportion to the extent of the area of the inner surface of the cavities of the heart at the commencement of their contraction, (each square inch of surface, according to the experiments of Hales, having a pressure upon it nearly equal to four pounds,) the more fre- quent contractions, where there is a smaller quantity of blood present in the heart at the commencement of each contraction, will not demand the same degree of muscular force for their performance, as if these had been less frequent. If, when the contractility of the heart became debilitated, the presence of a greater quantity of blood than usual in its interior had been necessary to stimulate it to contraction, and if the area of the inner surface of the cavities of the heart be in proportion to the quantity of blood contained there, it is apparent that the movements of the heart would have been much more rapidly and frequently arrested when its contractility became enfeebled, than they are under the actual arrangement. The influence of mental emotions upon the movements of the heart requires no illustration, for this is so universally experienced that in common language the heart is considered to be the seat of the affections and passions, and this has had a powerful influence upon the phrase- ology of all languages. In sanguine temperaments the heart gene- rally contracts more frequently than in phlegmatic temperaments. In women it is also generally a little quicker than in men. It varies very much in different classes of animals. Burdach* has given the following table col- lected from numerous sources, as an approxi- mative valuation of the frequency of the heart's action in various animals. Number of pulsations in a minute.f In the Shark 7 Mussel -15 Carp [[[ 20 Eel 24 Snake 34 Horse .*.*.* 36 Caterpillar 35 Bullock 38 * Physiologie, vol. iv. p. 251, t We cannot consider the number of pulsations of the heart in a minute given in the above t.iblc as by any means quite satisfactory. 'Ilio number of pulsations in the ox and horse is given on the aulliority of Vetel in Froricp, Notizcn, t. xxiv. p. 112. Other observers state the number of pulsa- tions in a minute at from 38 to 52 in the horse, and from 64 to 70 in the ox.
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