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' HEART. Ass 50 solete and to us in the present time almost Crab 50 incredible opinions, and the only use to wliich Butterfly 60 they are now applicable is to serve as beacons Goat 74 to keep us, in all our inquiries into the pheno- Sheep 75 mena of living bodies, within the strict path of Hedgehog 75 facts and obseiTation, and to forcibly impress Frog 77 upon us into what strange and fatal errors even Marmot 90 the brightest intellects may fall, when they Locust 90 leave the inductive method of investigation. Ape , 9o and wander into the alluring but dangerous Dormouse 105 regions of hypothesis. And the effects of these Cat 110 errors are only the more to be dreaded as they Duck 110 are often clothed in the most seductive in- Rabbit 120 genuity. It ought also still more forcibly to Menoculus Caster 120 inculcate upon us the important truth, which, Pigeon 130 though generally in our mouths, is not unfre- Guinea-pig 140 quently forgotten in practice,—that as the Hen 140 material world and all which it contains have Bremus terrestris 140 been placed by the Author of Nature under Heron 200 arbitrary and fixed laws, it is impossible to ex- Menoculus pulex 200 tend our knowledge of these by theorizing in For the effects of the respiration upon the the closet, and that this can only be effected by contractions of the heart, and the influence of the patient interrogation of Nature herself, the circulation of dark blood upon its irrita- It was not until the time of Senac and hility, see Asphtxia. Haller that accurate notions began to be enier- The came of the motion of the heart.—The tained on the nature of the heart's action, motion of the heart, and the constancy and The cause of the movements of the heart is regularity of its-movements, are circumstances distinctly referable to the same laws which so remarkable that they could not fail early to regulate muscular contractility in other ])arts of excite a deep interest among medical philo- the body, only modified to adapt it for the per- sophers when they had once turned their formance of its appropriate functions. Like attention to the explanation of vital phenomena, all the other muscles it is endowed with irrita- When we contemplate the heart commencing bility, which enables it to contract upon the its movements at an early period of foetal application of a stimulus. The ordinary and existence, and never resting from its apparently natural stimulus of the heart is the blood, unceasing toil until the latest moments of life, which is constantly flowing into its cavities, and when we remember the uniform and regu- The greater irritability of the inner surface over lar manner in which all its actions are accom- the outer is evidently connected with the plished—all conspiring for the proper per- manner in which the stimulus is habitually formance of the deeply important functions applied. When the blood is forced on more assigned to it, we are at first impressed with the rapidly towards the heart, as in exercise, its con idea that it is regulated by laws different from tractions become proportionally more frequent; similar textures of the body, and altogether and when the current moves on more slowly, peculiar to itself. It must have been under as in a state of rest, its frequency becomes pro- the influence of similar impressions that the portionally diminished. If the contractions of older medical philosophers approached this the heart were not dependent upon the blood, subject, and it is in this manner only that we and their number regulated by the quantity can account for many of the strange specula- flowing into its cavities, very seiious and in- tions on the heart's action which they have left evitably fatal disturbances in the circulation recorded. would soon take place. We find one sect attempting to explain it by As the heart continues to contract often for a a peculiar innate fire. Sylvius, the head of the very considerable time after the venae cava chemical sect, had recourse for its explanation have been tied, and after the blood has ceased to an effervescence excited by the intermixture to pass through its cavities, or after it lias been of the old and alkaline blood with the acid removed from the body, this has been supposed chyle and acid pancreatic lymph.* Descartes by some to indicate that there is something m supposed that a constant succession of explosions the heart's structure or m its vital properties occurred in the heart from steam generated which enables its movements to proceed mde- there, which propelled the blood through the pendent of all other circumstances. But m all body. Slahl got at once out of the difficulty these cases a stimulus has been applied in some by affirming that the heart was more particu- form or other to the heart. If the heart has larly under the guidance of the anima or soul, been allowed to remain in its place, though the But we cannot here dwell longer on these ob- circulation of the blood may have come to a stand, part of it may yet remain in the diHerent cavities of the orgaii; or if the pericardium has • In the same manner BovclH sayss, Constat y^^^^ opened the impression of the external ex dictis immecliiitam causain motivatn cordis esse . „ ' „ a Stimulus. The expe- ehullitioncm fcrmauvam tartarc. succ. sangumc. Jj^^^^^'; ^^^^ ^f,^J,^,. fo,,„,,,V men- excitiUam a commislionc succi sjurUiiosi a ncrvis nmenis 01 vvaiinti .uiu iiani-i ■ .i . . instillaii. I)c Molu Aniinaliuin, p. 97. tioiicil uiKMi the comparative irritability ol w>~_](https://iiif.wellcomecollection.org/image/b21908503_0038.jp2/full/800%2C/0/default.jpg)
