136 MOVEMENTS OF THE HEART. [BOOK i. 



ventricular orifices, and the auricular appendages are drawn inwards, 

 becoming smaller and paler. During the auricular systole, the ven- 

 tricles may be seen to become more and more turgid. Then follows, 

 as it were immediately, the ventricular systole, during which the 

 ventricles become more conical. Held between the fingers they are 

 felt to become tense and hard. As the systole progresses, the aorta 

 and pulmonary arteries expand and elongate, and the heart twists 

 slightly on its long axis, moving from the left and behind towards 

 the front and right so that more of the left ventricle becomes dis- 

 played. As the systole gives way to the succeeding pause or 

 diastole, the ventricles resume their previous form, the aorta and 

 pulmonary artery contract and shorten, the heart turns back to- 

 wards the left, and thus the cycle is completed. 



A more exact determination of the changes in the form and 

 position of the heart during a beat is attended with considerable 

 difficulties. The following experiment has been made with the 

 view of studying these changes without opening the chest and thus 

 without depriving the heart of its natural supports. If, in the un- 

 opened chest of a rabbit or dog, three needles be inserted through 

 the chest-wall so that their points are plunged into the substance 

 of the ventricle, one (B) at the base, close to the auricles, another 

 (A) through the apex, and a third (M) at about the middle of the 

 ventricle, all three needles will be observed to move at each beat of 

 the heart. The head of B will move suddenly upwards, shewing 

 that the point of the needle plunged in the ventricle moves down- 

 wards, whereas A will only quiver, and move neither distinctly up- 

 wards nor downwards. M will move upwards (and therefore its 

 point downwards), but not to the same extent as B. The nearer 

 to B, M is, the more it moves : the nearer to A, the less. After 

 the death of the animal, the needles, if properly inserted at first, 

 perpendicular to the chest, will be found with all their heads 

 directed downwards, indicating that the whole ventricle has been 

 drawn up by the contraction of the empty aorta and pulmonary 

 artery. 



The behaviour of the needles during the beat has been in- 

 terpreted as follows. At the systole the whole heart is thrust 

 downward by the elongation of the aorta and pulmonary artery. 

 The needle A at the apex however does not move its place, 

 because this downward movement is compensated by an upward 

 movement due to a shortening, during systole, of the longitudinal 

 diameter of the ventricle. The base in which the needle B is 

 plunged, moves downwards and draw r s closer to A, i.e. to the apex, 

 partly by the downward thrust from the elongation of the great 

 arteries and partly from the shortening of the ventricle itself. 

 Naturally the behaviour of the needle M is intermediate in 

 character, its downward movement being the more conspicuous 

 the nearer it is to B. The experiment then is taken to 

 prove that during the systole the ventricle shortens in its 



