1876.] 



of the Pulmonary Veins and Vena Cava. 



175 



One hour and twenty minutes after the thorax had been opened, and 

 about an hour and ten minutes after artificial respiration had been dis- 

 continued, the ventricle was still pulsating. Its rhythm was very irre- 

 gular. After one beat a pause of half a minute followed, and then 37 

 pulsations all together. One hour and forty minutes after opening the 

 thorax the inferior vena cava was noticed to be pulsating close to its 

 entrance into the auricle. A contraction spread like a wave from the 

 vena cava over the right auricle, and the appendix contracted after the 

 auricle itself. The superior vena cava also pulsated close to the heart. 

 The left auricle had ceased to pulsate a considerable time previously, and 

 the ventricles had also stopped. After the auricles had pulsated for a 

 while the ventricles again began. At one hour and fifty minutes after 

 opening the thorax the inferior vena cava was still pulsating. In ten 

 minutes more all movement had nearly ceased, and the observation was 

 discontinued. 



At one hour and fifty minutes after opening the thorax slight con- 

 tractions of the diaphragm were noticed. 



The striking points in this experiment are the contractions of the 

 pulmonary veins and the vena cava independently of the heart, the long 

 time during which they retained their irritability, and the continuance of 

 their pulsations after the other parts of the heart had ceased. The 

 pulsation of the pulmonary veins and of the ventricles at the same time, 

 while the auricles were motionless, is also deserving of attention. 



In another experiment we found the pulmonary veins pulsating in a 

 cat killed by a blow on the head. We have also seen pulsation in 

 animals killed in other ways ; but the proportion of cases in which we 

 have seen it to those in which we have not seen it is very small. On 

 looking through several modern text-books of physiology, we have failed 

 to find any mention of the rhythmical contractile power of the pulmonary 

 veins and vena cava; but the earlier anatomists were well acquainted 

 with it; and Haller* states that he has seen the pulmonary veins con- 

 tinue to pulsate for two hours, and that others had seen the vena cava 

 pulsate for three hours while all motion in the other cavities of the heart 

 had already ceased. Johannes Mtillert has also observed contractions of 

 the vena cava and pulmonary veins ; and in young animals the contrac- 

 tions of the pulmonary veins extend as far as they can be followed into 

 the lungs. 



The importance of contraction of the vena cava and pulmonary veins in 

 preventing reflux of blood into them during the contraction of the auricle, 

 under circumstances when any hindrance is opposed to the free flow of 

 its contents into the ventricle, is self-evident. Indeed HallerJ says 

 that it was supposed to exist by Senac, although he had not seen it. 



* ' Elementa Physiologia,' 1757, torn. i. pp. 410 & 399 ; and ' Memoires sur la 

 Nature sensible et irritable des parties du corps animal,' 1756, torn. iv. p. 4. 

 t Miiller's ' Physiology,' translated by Baly, 2nd ed. vol. i. p. 182. 

 X Op. cit. p. 410. 



