HEART. 



607 



fixed attachment, viz. the tendinous rings, white 

 by their other extremity part only are directly 

 attached to the tendinous rings, the other part 

 being loose, or at least only connected to the 

 tendinous rings through the lax chordae tendi- 

 neae and valves, it must follow that the force 

 with which the contraction takes place towards 

 the septal extremity must preponderate over 

 the other. If these bands of fibres had been as 

 closely connected to the tendinous rings at the 

 one extremity as at the other, then the force of 

 the contraction towards both would have been 

 equal ; but since this is not the case, the apex 

 must be carried forwards at the same time that 

 it is drawn upwards towards the base. This 

 forward motion may also probably be assisted 

 by another arrangement of the same fibres 

 which we have been describing; for some of 

 these muscular bands are attached by their 

 inner extremity to the anterior part of the left 

 auriculo-tendinous ring, so as to form loops, the 

 greater part of which lie more in front than be- 

 hind the axis of the heart, and may have a ten- 

 dency, when in a state of contraction, to draw 

 the apex forwards and upwards. Now when 

 we remember that by this elevation of the apex 

 forwards, the heart, before placed obliquely, 

 now becomes more horizontal, and conse- 

 quently more approximated to the walls of the 

 chest, the more particularly as the transverse 

 diameter of the chest diminishes rapidly as we 

 proceed from below upwards, we believe that 

 we have here sufficient to account for this im- 

 pulse against the chest. As the proximity of 

 the apex of the heart to the chest is affected by 

 the position of the body, as we have already 

 pointed out, this circumstance ought to be at- 

 tended to in judging of the strength of the im- 

 pulse of the heart. 



What parts of the heart most irritable. The 

 inner surface of the heart is considerably more 

 irritable than the outer. In experiments, when 

 the heart has become quiescent, and refuses to 

 obey a stimulus applied to the outer surface, it 

 frequently contracts readily for a short time 

 after this when air is introduced into its cavi- 

 ties, or when any other stimulant is applied to 

 its inner surface. After death the different 

 cavities of the heart generally lose their contrac- 

 tility in the following order, the left ventricle, 

 the right ventricle, the left auricle, and last of 

 all the right auricle.* And as the heart is gene- 

 rally the part of the body which shews the latest 

 evidences of contractility, the right auricle has 

 long received the name of ultimum moriens. 

 Haller supposed that the greater persistence of 

 contractility in the right side of the heart over 

 the left might depend on the circumstance that 

 the right side of the heart generally contains a 

 greater or less quantity of blood after death, 

 while the left side is generally empty. In this 



* There is occasionally considerable variety ob- 

 served in the order in which the different cavities 

 lose their contractility after death. The left ven- 

 tricle has been seen to contract after the right auri- 

 cle ; and Haller has observed in experiments upon 

 cats the irritability of the left auricle first cease. 

 In experiments upon dogs I have seen the ventri- 

 cles contract after the auricles had ceased to do so. 



manner the inner surfece of the right side of the 

 heart is subject after death to the presence of a 

 stimulant from which the left side is compara- 

 tively free. He put this opinion to the test by 

 performing repeatedly the following experi- 

 ment.* He emptied the right side of the heart 

 by the section of the pulmonary artery and 

 venae cavae, having previously retained the 

 blood of the left side by passing a ligature 

 around the aorta. The experiment succeeded 

 many times : the right auricle remained per- 

 fectly immoveable, and the only motion which 

 the right side retained arose from the connexion 

 of its fibres with those of the left ventricle. 

 The left auricle retained its movements for a 

 certain time, the ventricles during a longer 

 period, sometimes even for two hours. He adds, 

 we thus transfer from the right auricle to the 

 left ventricle the property of being the last 

 living part in the body, in preserving for it 

 during a longer period the irritation produced 

 by the contact of blood. These experiments 

 of Haller certainly shew that the left side of 

 the heart will continue to contract longer than 

 the right where it is subjected to a stimulant 

 of which the other is deprived ; but they do not 

 entitle us to conclude that the persistence of 

 their contractility is the same when placed un- 

 der similar circumstances. We have every 

 reason for believing that the right auricle is the 

 part of the heart which last loses its contracti- 

 lity. Indeed Haller himself confesses, that if 

 any part of the heart remains longer contractile 

 than another, it is the right auricle. Nysten,f 

 who performed a number of experiments upon 

 the comparative persistence of the irritability 

 in the different contractile parts of the body in 

 the human species, after decapitation by the 

 guillotine, and when the heart was conse- 

 quently emptied of its blood, obtained the fol- 

 lowing results upon the order in which the dif- 

 ferent parts of the heart lose their contractility : 

 1st, the left ventricle, the contractility of 

 which is annihilated much more quickly than 

 that of the other organs ; 2d, the right ventri- 

 cle, the movements of which generally continue 

 more than an hour after death ; 3d, the two 

 auricles, the right being of all the parts of the 

 heart that which preserves for the longest time 

 its contractile power. 



The stimulant used in these experiments was 

 galvanism. The greater persistence of the con- 

 tractility in the right auricle over the other parts 

 of the heart has been observed by other experi- 

 menters, after it had been cut from the body, 

 and consequently without any contained blood. 

 The particular part of the auricle which last 

 loses its contractility varies in different cases. 

 Sometimes the appendix is found contracting 

 when the rest of the auricle is quiescent; at 

 other times, and perhaps more frequently, those 

 parts of the auricle around the entrance of the 

 venae cavae retain their contractility longest. 



* Sur le mouvement du sang, p. 172. Similar 

 experiments were performed by Walther with the 

 same results : Experimenta de vivis animalibus, 

 p. 11, as quoted by Burdach. 



t Recherches de Physiologic, &c. p. 321. 



