HEART. 



603 



paticae.* Judging from the number of mus- 

 cular fibres which surround the termination of 

 the pulmonary veins in the human species, 

 we would expect these contractions to occur to 

 a greater extent in these veins than in the cavae. 

 These contractions in the veins must assist the 

 vis (i tergo, or the force with which the column 

 of blood flows along the veins towards the 

 heart, in limiting the regurgitation along these 

 during the contraction of the auricles. This 

 regurgitation along the veins appears to be to 

 a small extent only when the circulation is pro- 

 ceeding in a natural manner, but becomes con- 

 siderable where there is any impediment to the 

 free passage of the blood into the ventricles, 

 and when the blood becomes stagnated in the 

 veins. When the actions of the heart are en- 

 feebled, the contractions of the auricles are 

 slower, and may become more or less vermi- 

 cular, as I have myself occasionally observed. 

 Two or more contractions of the auricle may 

 also now be necessary before the languid ven- 

 tricle can be excited to contraction. When 

 the action of the heart is still more enfeebled, 

 particular portions only of the auricles con- 

 tinue to contract. According to the obser- 

 vations of Harvey, Lower, Senac, Haller, and 

 others, the contractions of the auricles are per- 

 formed with considerable force. 



Harvey states that he has observed that if the 

 finger is applied to the ventricles in those cases 

 where the action of the auricles continues after 

 the contractions of the ventricles have ceased, 

 a distinct beat is felt in the ventricle at each 

 stroke of the auricle ; and Senac, in quoting 

 this, adds (evidently from his own observation) 

 that it is similar to the pulse in the arteries. 

 Senac also states that if an opening be made 

 into the apex of the heart under those circum- 

 stances, a jet of blood rushes through it at 

 each stroke of the auricle. He, however, 

 admits that the contraction of the auricles in 

 these cases is not sufficient to dilate sensibly 

 the walls of the ventricles, but, of course, very 

 considerable allowance ought to be made for 

 the enfeebled state of the auricles at this stage 

 of the experiment. f In the experiments of 

 Dr. Hope, Mr. Carlisle, M. Bouillaud, and 

 the Dublin Committee for investigating the 

 cause of the sounds of the heart, the contrac- 

 tion of the auricles appeared to be compara- 

 tively trifling, and was most apparent in the 

 appendices. From my own observations upon 

 rabbits and dogs I am convinced that the au- 

 ricles contract considerably more when the 

 movements of the heart are proceeding in a 

 natural manner, than some of these last expe- 

 riments would lead us to believe, and that this 

 contraction is not confined to the appendix, 



* The contractions of the different parts of the 

 heart in cold-blooded animals have been observed 

 to occur in the following order : first, the termin- 

 ation of the large veins, then the auricles, then 

 the ventricles, and, lastly, the bulb of the aorta. 



f I have convinced myself of the accuracy of 

 these statements of Harvey and Senac in expe- 

 riments upon dogs opened soon after they had been 

 deprived of sensation. 



but extends over the whole auricle. When 

 the circulation through the lungs becomes im- 

 peded, the right ventricle is then unable to 

 empty itself, and the auricle of the same side 

 (and this is the one that is most generally ob- 

 served in such experiments) is consequently 

 impeded in its movements. The auricles do 

 not certainly exert the force or contract to the 

 extent which some have stated, do not ex- 

 pel the whole of their contents, and their 

 diastole is comparatively feeble; but that none 

 of the muscular fibres of the auricles are pas- 

 sive, but exert a force proportionate to their 

 strength, we have evidence both from expe- 

 riment and the effects of disease. In some 

 of those cases where an impediment to the 

 passage of the blood from the auricle to the 

 ventricle exists, all the muscular fibres of the 

 auricles become much increased in thickness 

 and in strength. As the left auricle has natu- 

 rally greater difficulties to overcome iu pro- 

 pelling its blood than the right, so we find that 

 the left auricle is considerably more muscular 

 than the right.* The appendix from its being 

 loose, and supplied by a band of longitudinal 

 fibres drawing it backwards, must enjoy a freer 

 motion than the other parts of the auricle. 



Systole and diastole of the ventricles. 

 When the heart is acting Vigorously, the con- 

 traction of the ventricles succeeds immediately 

 upon that of the auricles, so that they some- 

 times appear continuous ; or, in other words, 

 the sudden distention of the ventricles by the 

 blood propelled into them during the systole 

 of the auricles is rapidly followed by the con- 

 traction of the ventricles. The systole of the 

 ventricles must occur during the diastole of the 

 auricles. As we are only sensible of the sys- 

 tole of the ventricles from external examination 

 during life, the expression systole of the heart 

 is always employed as synonymous with the 

 systole of the ventricles. W T hen the action of 

 the heart is a little less active, an apparent in- 

 terval is observable between the completion of 

 the contraction of the auricles and the com- 

 mencement of the contraction of the ventricles, 

 the irritability of the ventricles being at this 

 time somewhat impaired, their contraction does 

 not so quickly follow their sudden distention. 

 The ventricles during their systole are dimi- 

 nished in all their dimensions; the apex is 

 drawn upwards to the base and tilted forwards 

 so as to strike the parietes of the thorax be- 

 tween the cartilages of the fifth and sixth ribs.f 



* In the case mentioned by Allan Burns, where 

 an ossific deposit covered the whole surface of the 

 ventricles, so as to entirely, or nearly entirely, pre- 

 vent their action, the auricles must have per- 

 formed part of their functions for some time before 

 death. In one of the experiments of Dr. Wil- 

 liams, of London, upon asses, he observed the 

 circulation along the arteries continue although 

 the ventricles were quiescent, and the auricles 

 alone contracted. 



t " Dr. C. J. B. Williams has, in a lecture lately 

 published in the Medical Gazette (July 28, 1838, 

 p. 692,) pointed out that, during a deep inspira- 

 tion, the ribs are elevated without raising the heart 

 in the same degree, and the impulse may be felt 



