602 



HEART. 



It may be supposed that the relative size of 

 the auriculo-ventricular orifices to the length of 

 the lips of the valves would not admit of their 

 apices being brought together in the form of a 

 cone as described, but it must be remembered 

 that from the course of the muscular fibres in 

 the immediate neighbourhood of those open- 

 ings, their areas must be diminished during 

 the systole of the heart. There is at least one 

 thing certain connected with the action of these 

 valves, viz. that the contraction of the musculi 

 papiilares can never cause the valves to strike 

 the inner surface of the ventricle and produce 

 a sound as has been supposed. 



The manner in which the semilunar valves 

 at the origin of the aorta and pulmonary artery 

 perform their office is entirely mechanical and 

 easily understood. During the systole of the 

 heart they are thrown outwards from the axes 

 of these vessels ; but during its diastole, when 

 part of the blood driven into the artery would 

 fall back into the ventricles, these valves are 

 thrown inwards and obstruct completely the 

 whole calibre of the arteries. In all probability 

 the sinuses of Valsalva placed behind these 

 valves contain a certain quantity of blood even 

 during the systole of the heart, and this re- 

 acting upon the valves through the agency of 

 the elasticity of the arteries brought into opera- 

 tion at the termination of the systole, materially 

 assists in producing the more rapid arid certain 

 action of the valves. 



Movements of the heart. The heart is a 

 muscle of involuntary motion, being, for the 

 wisest of purposes, placed beyond the direct 

 control of volition. The case of Colonel 

 Townshend* is of too obscure a nature to 

 entitle us to found upon it an opposite doc- 

 trine, more particularly as it is at direct variance 

 with every other fact or observation. 



The movements of the heart, when the body 

 is at rest or in a state of health, proceed with- 

 out our consciousness. In certain cases of 

 disease they are attended by uneasy feelings, 

 but they are never at any time or under any 

 circumstances dependent upon sensation for 

 their continuance. 



It is not so easy a matter as may at first be 

 imagined to ascertain the order of succession 

 in which the different cavities of the heart con- 

 tract and dilate, and the different circum- 

 stances which attend these movements, even 

 by experiments on living animals, more par- 

 ticularly the warm-blooded animals ; for if the 

 heart when exposed is acting vigorously and 

 rapidly, every one who has examined for him- 

 self must have felt the exceeding difficulty of 

 following and analysing these movements by 



right ventricle is, in any material degree, tempo- 

 rarily distended or permanently dilated, the heart 

 and lungs are relieved by a considerable reflux of 

 the ventricle's contents into the auricle and sys- 

 temic veins." In experiments upon the lower 

 animals I have repeatedly seen the right ventricle, 

 when gorged with blood and acting feebly, empty 

 itself through an opening in the jugular vein. 

 Edinb. Med. and Surg. Journ. 1836. 



* Cheyue's English Malady, p. 307. 1734, 

 London. 



the eye. If, on the other hand, the animal 

 has become debilitated and the movements of 

 the heart languid, these are apt to deviate from 

 their natural order, and to be performed in an 

 irregular and unnatural manner.* It is in this 

 way that we can account not only for the dis- 

 crepant statements of the older observers, but 

 also for the very frequent announcement of 

 new views on this subject which appear in the 

 medical periodicals of our own day. As we 

 will find that many of these theories connected 

 with the physiological actions of the heart even 

 in the present day, have been founded upon 

 false notions of the normal anatomy and na- 

 tural movements of the organ, and only require 

 a reference to these for their full and satis- 

 factory refutation, it will be necessary that we 

 attend particularly to the manner in which 

 these different contractions and relaxations suc- 

 ceed each other, and the visible phenomena 

 by which they are accompanied, as observed 

 by the most accurate experimenters. 



When the heart of a living animal is ex- 

 posed and the organ is acting in a natural 

 manner, the auricles are observed to become 

 distended with blood, then to contract rapidly 

 and simultaneously, and propel part of it into 

 the ventricles; this is accompanied with a 

 corresponding enlargement of the ventricles, 

 which is immediately followed by their simul- 

 taneous contraction and the propulsion of their 

 blood along the large arteries : then follows a 

 pause, during which the auricles become gra- 

 dually distended by the blood flowing along 

 the veins. When the auricles are filled, they 

 again contract, and the same train of pheno- 

 mena just described occur in uniform succes- 

 sion. 



Systole and diastole of the auricles. The 

 contraction or systole of the auricles is pre- 

 ceded by their relaxation or diastole. During 

 the diastole the auricles become distended with 

 the blood flowing along the veins. The com- 

 mencement of the diastole occurs during the 

 contraction of the ventricles; the latter part 

 corresponds to the pause in the heart's action, 

 and to the interval between the recurrence of 

 the sounds of the heart, and is more or less 

 long in proportion as the blood flows more or 

 less rapidly along the veins. 



The systole of the auricles is performed with 

 great rapidity when the action of the heart is 

 still vigorous, and appears to be effected by 

 the simultaneous contraction of all its fibres. 

 The terminations of the cavae and pulmonary 

 veins are seen to contract simultaneously with 

 the fibres of the auricles, but sometimes they 

 are seen to contract previous to the auricles, 

 into which they expel their blood. In the cold- 

 blooded animals this contraction of the ter- 

 minations of the large veins extends over a 

 greater surface, and is visible in the venae he- 



* The illustrious Harvey thus describes the dif- 

 ficulties which he experienced in his first attempts 

 to analyse the movements of the heart: " ita ut 

 modo hinc systolem, illinc diastolem, modo e con- 

 tra, modo varies, modo confusos fieri motus me 

 cxistimarem cernere." 



