G04 



HEART. 



The parietes of the ventricles at tliis time are 

 firm and resisting, and present some ruga; on 

 their outer surface. Ilaller* states that though 

 the principal movement of the ventricles du- 

 ring their systole is from the apex upwards, 

 yet he has sometimes observed a slight but dis- 

 tinct movement from the base downwards. The 

 contraction of the ventricles is performed with 

 great force, and, when vigorous, appears to be 

 accomplished by the simultaneous action of all 

 its fibres; but at other times, when it has be- 

 come enfeebled, it has been observed to com- 

 mence at the apex and extend itself upwards. 



The diastole of the ventricles consists of two 

 distinct stages. The first, which immediately 

 follows its systole, is sudden, the apex being 

 pushed downwards and apparently passing 

 deeper into the chest, and is occasioned by the 

 return of the heart to its state of rest. The 

 second is also sudden, and attended by a rapid 

 but not very extensive enlargement of the heart 

 in all its dimensions. The parietes of the 

 heart are soft and flaccid, and their external 

 surface smooth during their diastole. The 

 diastole of the heart is performed with con- 

 siderable force, so that Pechlin, Perrault, llam- 

 borgcr, and others long ago maintained that 

 this equally with the systole is the result of a 

 vital action. This opinion was again revived 

 by Bichat, Dumas, and their followers, and is 

 still introduced by some into the discussions 

 upon the movements of the heart. Before 

 we can admit an opinion of this kind, it 

 would be necessary that very strong evidence 

 be adduced in its favour, as it is at perfect 

 variance with all that we know of the arrange- 

 ment of the fibres of the heart, and of the 

 laws of muscular contractility.-)- 



OesterreicherJ has performed the following 

 experiment, which appears nearly decisive on 

 this point. When a body is placed on the 

 heart of a frog heavy enough to press it flat, 

 but sufficiently small to allow the heart to be 

 observed, it will be seen that the body will be 

 lifted during the contraction of the heart, but 

 that during its extension it will remain flat. 

 From this it appears that the extension of the 

 heart after the contraction is not a muscular 

 act. The diastole of the heart depends then 

 upon two circumstances. 1st, Upon the na- 

 tural elasticity of the organ, which it possesses 

 in common with every other muscle, and by 

 which it instantly resumes its state of rest as 

 soon as its contraction has ceased. This, which 

 is usually termed the relaxation of a muscle in 

 whatever part of the body it occurs, must be 

 expected to be more energetic in the heart than 



below the sixth rib. On the other hand, when the 

 rib arc depressed, as during a deep expiration, 

 the apex of the heart may be felt beating between 

 the fourth and fifth ribs." 



* El. Phys. torn. i. p. 400. 



t Scharsclimid supposed that certain pretended 

 longitudinal fibres^by shortening the heart enlarged 

 its cavities, while the transverse fibres by contract- 

 ing separately diminish its capacity. 



t Muller's Handbucb dvr Physiologic des men- 

 schcn, Erstcr Baud, p. 163. 



in the muscles of voluntary motion, as from 

 the arrangement of its fibres a great part must 

 be more strongly compressed. This occurs 

 during the first of the two stages into which 

 we divided the diastole. 2d, Upon its sudden 

 distention during the contraction of the auricles, 

 when we have every reason to believe that the 

 ventricles are completely passive. This con- 

 stitutes the second stage of the diastole. The 

 blood must then pass from the auricles into 

 the ventricles during each diastole at two dis- 

 tinct periods of time, corresponding to these 

 two stages. During the first stage, or the re- 

 laxation of the ventricles, it flows from the 

 auricles to fill up the vacuum produced in their 

 interior; while, during the second stage, it is 

 forcibly propelled by the auricles. It would 

 be difficult to estimate the relative proportion 

 of these two quantities of blood. Those who 

 suppose that the contraction of the auricles is 

 feeble must consequently believe that most of 

 the blood passes from the auricles into the ven- 

 tricles during the first stage. 



It has been long disputed whether or not the 

 ventricles empty themselves completely during 

 each systole. It is very difficult to perceive 

 anything like correct data upon this point in 

 the warm-blooded animals with opaque hearts; 

 but reasoning from analogy, from what we see 

 in the cold-blooded animals whose hearts be- 

 come quite pale during each systole, (not, as 

 Harvey supposed, from the blood being pressed 

 out of its parietes, but from the blood in its 

 cavity, seen through its transparent sides, being 

 almost entirely expelled during its systole,) 

 we would be inclined to believe that little 

 blood remained after each systole in the active 

 state of the organ, while we can easily sup- 

 pose that a greater or less quantity is left after 

 each contraction when the organ is less vi- 

 gorous. 



It was the subject of a violent dispute at the 

 commencement of the last century between the 

 Montpellier and Parisian anatomists and phy- 

 siologists, whether or not the heart became 

 shortened or elongated during its contraction. 

 In all the warm-blooded animals at least it 

 undoubtedly becomes shortened.* We may at 

 the same time state that the obliteration of the 

 cavity of the ventricle depends much more upon 

 the approximation of its sides than the drawing 

 up of the apex. 



Impulse of the heart, It has been at various 

 times, and still is by some late and modern 

 experimenters,f maintained that the apex of 

 the heart strikes the parietes of the thorax during 



* The authoiity of Harvey has been quoted in 

 favour of the opinion that the heart becomes elon- 

 gated during its contraction, and certainly in one 

 part of his work it is distinctly stated, that it is so 

 to a certain extent : " Undique contrahi magis 

 vero secundum .latera ; ita uti minores magnitu- 

 dinis ct l(ni{iiiucitluin t ct collectum appareat." 



t Pigeaux, Stokes, Jiurdach, and Beau. Dr. 

 Corrigan has, much to his credit, publicly re- 

 nounced his previously published opinions on this 

 question, after more accurate observations had con- 

 vinced him of his error. 



