SUCCESSION OF THE MOVEMENTS OF THE HEART. 43 



at right angles to and touching the point during the diastole, and a small silver tube was 



introduced through the walls into the left ventricle. At each contraction a jet of 



blood spurted out through the tube, and the point of the heart receded from the knife 



about an eighth of an inch. The animal experimented upon was a dog, a little above 



the medium size. These simple experiments demonstrate that, in the dog at least, the 



ventricles shorten during their systole. The ar- 



rangement of the muscular fibres is too nearly iden- 



tical in the heart of the warm-blooded animals to 



leave room for doubt that it also shortens in the 



human subject. The error which has arisen in this 



respect, and which obtained in our first experiments 



made in 1861, is due to the locomotion and pro- 



trusion of the entire organ, so as to make the point 



strike against the chest. A little reflection indicates 



the mechanism of this phenomenon. During the 



intervals of contraction, the great vessels, particu- 



larly the aorta and pulmonary artery, which attach 



the base of the heart to the posterior wall of the 



FIG. 18. Diagram of the shortening of 

 thorax, are filled but not distended with blood ; at the ventricles during systole. 



each systole, however, these vessels are distended The drtt " f the 



to their utmost capacity ; their elastic coats permit 

 of considerable enlargement, as can be seen in the living animal, and this enlarge- 

 ment, taking place in every direction, pushes the whole organ forward. We have 

 also considerable locomotion of the heart from recoil. It is for this reason that, 

 observing the heart in situ, the ventricles seem to elongate. It is only when we 

 examine the heart firmly fixed, or contracting after it is removed from the body, 

 that we can appreciate the actual changes which occur in the length of the ventricles. 

 During the systole the ventricles are shortened and are narrowed in their transverse 

 diameter, but their antero-posterior diameter is slightly increased. 



In addition to the marked changes in form, position, etc., which the heart undergoes 

 during its action, we observe, on careful examination, that the surface of the ventricles 

 becomes marked with slight longitudinal ridges during the systole. This was not noted 

 by Harvey, but is mentioned by Haller. 



Impulse of the Heart. Each movement of the heart produces an impulse, which can 

 be readily felt and sometimes seen, in the fifth intercostal space, a little to the left of the 

 median line. Vivisections have demonstrated that the impulse is synchronous with the 

 contraction of the ventricles. If the hand be introduced into the chest of a living animal, 

 and the finger be placed between the point of the heart and the walls of the thorax, 

 every time that we have a hardening of the point, the finger will be pressed against the 

 side. If the impulse of the heart be felt while the finger is on the pulse, it is evident 

 that the heart strikes against the thorax at the time of the distention of the arterial 

 system. The impulse is due to the locomotion of the ventricles. In the words of Harvey, 

 " the heart is erected, and rises upwards to a point, so that at this time it strikes against 

 the breast and the pulse is felt externally." In the case of the son of the Viscount Mont- 

 gomery, already referred to, Harvey gives a most graphic description of the manner in 

 which the heart is u retracted and withdrawn " during the diastole, and " emerged and 

 protruded " during the systole. 



Succession of the Movements of the Heart. We have already followed, in a general 

 way, the course of the blood through the heart and the successive action of the various 

 parts ; but we have yet to consider these points more in detail, and to ascertain, if 

 possible, the relative periods of activity and repose in each portion of the organ. 



