608 



HEART. 



Harvey and some of the older anatomists ob- 

 served the movements of the venae cavae to 

 continue in some of the lower animals after the 

 auricles had ceased to move. The apex of the 

 ventricles frequently remains longer contractile 

 than the rest of the ventricle. Haller suggested 

 that this might depend on the remaining blood 

 gravitating to the apex, and there acting as a 

 stimulant. 



Duration of contractility after death. In 

 the cold-blooded animals the heart may be 

 made to contract fourteen, twenty, thirty-four 

 hours, or even longer after death. In warm- 

 blooded animals the heart remains contractile 

 for a much shorter period after death than in 

 cold-blooded animals. Haller found the heart 

 contractile in a warm-blooded animal in one 

 case four hours after death, and in another 

 seven hours. He sometimes observed it to 

 cease before the vermicular motion of the intes- 

 tines. Wepfer found it irritable in a dog six 

 hours after death. Nysten, who attended par- 

 ticularly to this subject, found in one of his 

 experiments on the human subject, that the 

 ventricles refused to contract upon the applica- 

 tion of galvanism one hour after decapitation, 

 while the auricles continued contractile for 

 seven hours five minutes after death.* In ano- 

 ther case the right auricle was still contractile 

 eight hours after death ;f and in a subsequent 

 case which he relates, it remained contractile in 

 the neighbourhood of the entrance of the supe- 

 rior cava sixteen hours and a half after death .J 

 In the Mammifera, Nysten found that the left 

 ventricle often refused to contract thirty minutes 

 after death ; that the right ventricle retained its 

 contractility two hours, and sometimes longer, 

 while the right auricle was not quiescent upon 

 the application of the galvanism until eight 

 hours after death. 



He found it to vary in birds according to the 

 degree of muscular activity which they enjoyed 

 during life. In those of high flight, and which 

 exercise great muscular contractility during life, 

 and have a rapid circulation, as the sparrow- 

 hawk, the irritability of the heart and other 

 muscles becomes much more speedily exhaust- 

 ed than in those the movements of which are 

 comparatively slow and feeble, as in most domes- 

 tic fowls. Nysten supposes that the explana- 

 tion of the greater persistence of contractility of 

 the right ventricle over the left lies in the cir- 

 cumstance that the left acts with greater vigour 

 during life, thus referring it to the important 

 general law which he has established by his 

 experiments upon the comparative excitability 

 of the muscular tissue in the various classes of 

 animals, that the duration of the contractility 

 after death is in the inverse ratio of the muscu- 

 lar energy developed during life. || Before we 



* Op. cit. p. 316. 



t Page 318. 



j In these experiments all the other parts of the 

 body lost their contractility before the right auricle. 



Op. cit. p. 349. 



\\ Dr. Marshall Hall (Phil. Trans. 1832) has 

 more lately laid it down as a general law that the 

 irritability of the heart and other muscles is in the 

 inverse ratio of the oxygen consumed in respiration. 



could admit this explanation, it would be ne- 

 cessary to show, what we believe it will be 

 found impossible to do, that the left ventricle, 

 apart from its greater quantity of muscular fibre, 

 exerts greater strength or exhibits more ener- 

 getic contractions during life than the right 

 ventricle. In young animals, immediately after 

 birth, the contractility of the heart continues 

 longer after death than in the adult animal. 

 We would expect this to be most apparent in 

 those which are born with their eyes shut, as 

 puppies and kittens, and in those birds which 

 are hatched without feathers, since these ani- 

 mals at that period of life approach in their 

 physiological conditions to the cold-blooded 

 animals. There is a curious circumstance 

 stated by Mangili, and confirmed by Dr. Mar- 

 shall Hall, connected with the hybernation of 

 animals, that if those mammalia which hyber- 

 nate are killed while under a state of lethargy, 

 the heart and other muscles remain contractile 

 for a longer period than when they are killed 

 in a state of activity, thus resembling, when 

 under the influence of this lethargy, in this as 

 in many other respects, the physiological con- 

 dition of the cold-blooded animals. The con- 

 tractions of the heart may frequently be renewed 

 by the application of warmth after they have 

 apparently ceased. I have repeatedly observed 

 the fact which has been stated by Haller and 

 Nysten, that when any of the cavities of the 

 heart become congested with blood, their con- 

 tractility becomes arrested, and, in their opi- 

 nion, extinguished.* I have also found that 

 unloading the right side of the heart soon after 

 the congestion has taken place, which can be 

 done in many cases by opening the external 

 jugular vein, acts as a valuable adjuvant under 

 certain circumstances in renewing the heart's 

 action. These it would be out of place to dis- 

 cuss here ; but I may state that it appears to 

 me to be principally useful in certain cases of 

 poisoning, in asphyxia, and after the accidental 

 entrance of air into the veins. Since the intro- 

 duction of a considerable quantity of air into 

 the veins produces death by mechanically ar- 

 resting the movements of the right side of the 

 heart, we believe that circumstances may occur 

 in which the surgeon may be justified in intro- 

 ducing a tube into one of the large veins pass- 

 ing into the upper part of the chest, and suck- 

 Various experimenters distinctly show that as we 

 descend in the scale of animals the quantity of oxy- 

 gen consumed diminishes, and that Birds consume 

 more than Mammalia. Dr. Edwards has also 

 shown that the young of the Mammalia deteriorate 

 the atmospheric air less rapidly than the adult ani- 

 mals ; and the experiments of Mangili and Prinella 

 prove that hybernating animals, when in a state of 

 lethargy, consume exceedingly little oxygen, so 

 that there is evidently some relation between irri- 

 tability'and the quantity of oxygen consumed in re- 

 spiration ; but for the proof that the irritability is 

 exactly in the inverse ratio of the respiration, we 

 must wait for Dr. Marshall Hall's promised experi- 

 ments. 



* Haller supposed that this was effected, as must 

 be if allowed to continue for any length of time, 

 by the too great distension of the muscular fibres, 

 in the same manner as distension of the bladder 

 produces paralysis of its fibres. 



