ACTION OF THE HEART. 



301 



tricles is completed, a sudden movement of relaxation takes place similar to 

 that of an elastic bag when released from pressure, and this is followed by a 

 brief interval of complete rest; during which both Auricles and Ventricles an- 

 rapidly tilling with blood ; contraction then again recurs. During the systole 

 the heart becomes more globular, or, perhaps more correctly speaking, more 

 conical in form. The chief movement observable in the Auricles is the sud- 

 den retraction of the appendices, which almost instantly become refilled with 

 blood as the ventricles contract. The contraction of the two ventricles seems 

 to take place simultaneously towards a centre or point of rest, which in the 

 right ventricle, where the action is most easily observed, is situated about the 

 middle of its length, near the septum and opposite the attachment of the 

 anterior papillary muscle (Sibson). The base of the heart descends rather 

 more than the apex ascends. There is a slight twisting movement of the 

 whole heart during the systole, both on its longitudinal and on its transverse 

 axis. By its rotation on its transverse axis the apex of the heart is tilted 

 forwards; by its rotation on the long axis the left ventricle, which during 

 the diastole looks backward, is turned forwards. The combination of the 

 two movements gives to the apex a twisting movement from left to right and 

 forwards. The apex beat is felt between the 5th and 6th ribs, and is caused 

 by a part just above the apex. In the act of contraction the heart may be 

 felt to become hard. During the diastole the heart undergoes a change in 

 form, the converse of that which has been above described. The impulse 

 is felt over every part of the Ventricles during their contraction, but most 



FIG. 122. 



forcibly over their centre. The experiments of MM. Chauveau and Marey, 1 

 with a peculiar form of Cardiograph, represented in Fig. 122, in which levers 

 of extreme lightness register the undulations of the air contained in elastic 

 sacs applied to the surface of the Heart and Thorax, show clearly the 

 sequence and duration of the movements of the Auricles and Ventricles, and 

 the coincidence of the impulse with the contraction of the Ventricles (Fig. 

 124). The Cardiograph, as modified by Sanderson, consists of a hollow disk 

 of brass, the front of which is closed by a thin india-rubber membrane called 

 a tympanum. To the brass back a flat steel spring is screwed, which is bent 

 twice at right angles in such a way that its extremity is opposite the centre 

 of the tympanum. The extremity is perforated by a steel screw, the point 



1 Anna!, des Scien. Nat., 4th ser., Zool., torn, xvii, p. 374; and Mem. de la Soc. 

 de Biol., ser. iii, tom.iii, pt. ii, 1802, p. 1. For other Cardiographic tracings and ac- 

 counts of the instruments employed, see A. H. Garrod in Journ. of Anat. and Phys., 

 Nov. 1870, and Rutherford's lectures in Lancet, 1871-72. 



