THE CARDIOPNEUMATIC MOVEMENT. 121 



THE CARDIOPNEUMATIC MOVEMENT. 



As the heart during systole occupies a smaller space in the interior 

 of the thorax than during diastole, air must enter the thorax as the heart 

 contracts if the glottis is open. When, however, the heart relaxes in 

 diastole, air must escape through the open glottis as the heart enlarges. 

 A similar influence must be due to differences in the degree of fulness 

 of the intrathoracic vascular trunks. This cardio pneumatic movement is, 

 in animals in which during hibernation the respiratory movements are 

 suspended, of the greatest importance for the maintenance of metabolism, 

 which continues in moderate degree. The interchange of carbon and 

 oxygen in the lungs is greatly facilitated by agitation of the pulmonary 

 gases, and this interchange suffices to aerate the blood passing slowly 

 through the lungs. 



Method. The movement may be demonstrated by means of: 



1. The manometric flame, the trachea of a curarized animal being opened 

 and connected with a bifurcated tube, one branch of which leads to the gas-tubing 

 and the other to a small gas-flame. As in this manner a free communication is 

 established between the organ of respiration and the gas-supply, the movements 

 of the heart will be transmitted to the gas-flame. In man it is possible, after a 

 little practice, to transmit the movement in an analogous manner to the gas- 

 flame through one nostril after closure of the other nostril and the mouth, or 

 through the mouth after closure of the two nostrils. 



2. By acoustic means, namely by introducing an exceedingly sensitive whistle 

 constructed from a hollow sphere, in animals into the trachea divided transversely, 

 in man especially when the heart's action is stimulated into the mouth, after 

 closure of the nose, it is possible to demonstrate the cardiopneumatic movement, 

 particularly if the whistle is blown continuously and with extreme softness. 



3. By means of the cardiopneumograph (Fig. 35). This consists of a tube, 

 which is held between the lips (D), while respiration is suspended, the glottis is 

 opened and the nostrils are closed. The extremity of the tube, which is bent 

 upward, perforates a small plate (T) , over which a delicate membrane consisting 

 of a mixture of collodion and castor-oil is stretched with moderate force. From 

 the center of the membrane a glass thread (H) passes over the free edge of the 

 plate and is provided at its extremity with a delicate hair, which registers the 

 movements of the membrane on a tablet (S) moved by clockwork. Every ex- 

 piratory movement of air causes depression and every inspiratory movement 

 elevation of the recording point. Attached to the side of the tube is a valve 

 with a sufficiently large opening (K) and which may be opened to allow the indi- 

 vidual to breathe freely during a pause. The periodic movements of the respiratory 

 gases propelled by the heart-beat cause associated movements in the delicate 

 collodion membrane, and these are in turn transmitted to the recording lever. 



The graphic curve (Fig. 35, A and B) exhibits the following details: 



1 . The respiratory gases undergo a sudden expiratory movement coincidently 

 with the first sound of the heart because at the instant of the ventricular 

 systole the blood from the ventricles has not yet left the thorax, while venous 

 blood is pouring into the right auricle through the venae cavae, and because in the 

 same instant of systole the dilating branches of the pulmonary artery must cause 

 approximately the same quantity of air to escape from the nearest air-passages 

 in the lungs. In fact, the blood contained in the right auricle does not leave the 

 thorax at all; it is only transferred to the lesser circulation. This expiratory 

 movement would often be greater if it were not limited by two factors, namely: 

 (a) because the muscular mass of the ventricle occupies a somewhat smaller vol- 

 ume during contraction, and (6) because the thoracic cavity in the region of the 

 fifth intercostal space is somewhat enlarged outwardly by the apex-beat. 



2. There follows immediately a marked inspiratory movement of the respira- 

 tory gases, in consequence of which the large ascending limb of the curve is re- 

 corded. As soon as the blood- wave has advanced from the root of the aorta to 

 those portions of the large arteries that lie at the boundaries of the thoracic 

 cavity, a much larger quantity of arterial blood begins to leave this cavity, because 

 venous blood is at the same time being poured into it through the venae cavae. 



