656 VASCULAR SYSTEM IN ASPHYXIA. [BOOK n. 



by the fact that if the artificial respiration be resumed while this 

 fall is taking place, or when it has taken place, the pressure at once 

 rises again very rapidly in proportion as the heart recovers its 

 power, shewing that the vaso-constriction is still at work. The 

 diminished energy of the heart-beat is due to the nutrition of 

 the cardiac tissue suffering under the increasing venosity of the 

 blood ; and if the air continue to fail to get access to the blood in 

 the lungs, the heart finally ceases to beat. The right side, by 

 virtue of what appears to be an inherent quality, continues to beat 

 rather longer than the left ; but the pulmonary peripheral resist- 

 ance continuing, the efforts of the right ventricle to empty itself 

 are ineffectual; and, since the venous system continues to be 

 overfilled, it is the right side of the heart which is at death 

 especially distended. 



The failure in the heart is as we have said chiefly due to the 

 too venous blood interfering with the nutrition of the cardiac sub- 

 stance ; but this injurious influence is aided by the distension of 

 the cardiac cavities ; this, up to a certain limit, beneficial to the 

 vigour of the cardiac stroke, when it passes those limits becomes 

 harmful ; and the over-distended ventricles, which at the close of 

 asphyxia have ceased to beat, may resume their beat if they be 

 artificially relieved of their too great load of blood. 



If, before the fatal end is reached, the artificial respiration be 

 resumed, the restored condition of the blood at once makes itself 

 felt in an improved heart-beat. Both ventricles beat vigorously 

 again, discharging the contents of their distended cavities; and 

 the splanchnic vaso-constriction still, as we have said, continuing, 

 the systemic blood-pressure rises rapidly and indeed may reach a 

 height greater even than during the asphyxia. The resistance in 

 vascular areas other than the splanchnic remaining low, a large 

 quantity of blood is driven by the high pressure into these areas, 

 into the skin for instance, as indeed is shewn by the plethys- 

 mograph, and through them into the venous system. The in- 

 creased beat of the right ventricle, aided by the free venous flow 

 into it, produces a rise in blood-pressure in the pulmonary artery 

 similar to that in the aorta. Later on, the blood having become 

 normal as regards its gases, the increased resistance in the splanchnic 

 area gives way, the vessels in this area return to their normal tonic 

 condition, and the vessels in other areas returning also from their 

 dilated to their normal tonic condition, the systemic blood-pressure 

 returns to its normal height as also does that of the pulmonary 

 artery. 



387. In an animal, not under urari, and dying by asphyxia 

 . in an ordinary way, the phenomena are in the main the same as 

 those of which we have just given a sketch ; but as we have said 

 the exaggerated respiratory movements, and especially the con- 

 vulsive struggles, in which these culminate, introduce complications. 

 Perhaps the most marked of these is the increased venous inflow to 



