172 THE MOTION OF THE BLOOD. 



Though this is generally allowed, Haller remarks that in the 

 frog also, which has a straight aorta, the apex of the heart moves 

 forwards during the contraction 11 ; and, in opposition to Blumen- 

 bach's explanation, some say that while the heart of a dog, rabbit, 

 &c., continues to palpitate, after being extracted from the chest, 

 the apex is lifted up at each contraction of the empty ventricles.' 



The occurrence is ascribable likewise, in some measure, to the 

 distension of the auricles ; for Haller found the apex give the 

 usual stroke at the nipple, on his distending the left auricle with 

 air k , and Senac 1 has shown a similar influence from the right 

 auricle also. When the ventricles are contracting, no blood can 

 leave the auricles, which must, therefore, become distended by 

 its accumulation. 



It is equally evident, that, when the ventricles dilate again, the 

 blood must rush into them from the auricles. 



These considerations show, without experiment, that the auri- 

 cles and ventricles are always in opposite states, that, when the 

 ventricles are in systole, the auricles are in diastole, and vice 

 versa. 



On applying the ear or a stethoscope to the region of the heart, 

 two successive sounds may be distinctly perceived. At the mo- 

 ment of the stroke of the heart against the ribs (which stroke 

 may be felt more strongly if the person lies on the left side), and 



" When the blood is forced into the arteries, their curvatures, near where they 

 issue from the ventricles, are from their distension lengthened and extended to- 

 wards straight lines ; and, causing the heart to participate in their motions, com- 

 pel it to describe the segment of a circle, when the apex moving atlantad and 

 sinistrad, is made to strike against the left side. The same kind of motion hav- 

 ing also been observed by the celebrated Haller, in distending the left or sys- 

 temic auricle, it must follow, that the stroke which is given to the side, may be 

 the effect of two distinct causes, either acting separately, or in combination : but 

 acting on a heart obliquely situated, as ours is, in the cavity of the thorax, where 

 the aspect of the base is atlantad and dextrad, and that of the apex sinistrad and 

 sacrad. In combination, as the first of the two, by removing the pressure, will 

 facilitate the influx of the venous blood into the left or systemic auricle, which is 

 situated dorsad ; so the second, by the influx of blood into the auricle, will con- 

 tribute in its turn to facilitate the circular motion of the heart, proceeding from 

 the arteries." The Muscular Motions of the Human Body, p. 567. 



h El. PhysioL t. i. p. 394. 



1 Professor Mayo, Outlines of Human Physiology. 1827. p. 68. Dr. Hope, &c. 



k 1. c. ibid, where he refers to Senac and Ferrein. 



1 Traite du Cocur, p. 357. 



