THE HEART. 273 



heard a slight friction sound, produced by the collision of the point 

 of the heart against the parietes of the chest. This sound, which is 

 heard in the fifth intercostal space, is very faint, and is more or less 



Fig. 84. 



masked by the strong valvular sound which occurs at the same 

 time. It is different, however, in character from the latter, and 

 may usually be distinguished from it by careful examination. 



The movements of the heart during the time of a pulsation are 

 of a peculiar character, and have been very often erroneously 

 described. In fact altogether the best description of the move- 

 ments of the heart which has yet appeared, is that given by "Wil- 

 liam Harvey, in his celebrated work on the Motion of the Heart and 

 Blood, published in 1628. He examined the motion of the heart 

 by opening the chest of the living animal ; and though the same or 

 similar experiments have been frequently performed since his time, 

 the descriptions given by subsequent observers have been for the 

 most part singularly inferior to his, both in clearness and fidelity. 

 The method which we have adopted for examining the motions of 

 the heart in the dog is as follows : The animal is first rendered 

 insensible by ether, or by the inoculation of woorara. The latter 

 mode is preferable, since a long-continued etherization seems to 

 exert a sensibly depressing effect on the heart's action, which is 

 not the case with woorara. The trachea is then exposed and 

 opened just below the larynx, and the nozzle of a bellows inserted 

 and secured by ligature. Finally, the chest is opened on the me- 

 dian line, its two sides widely separated, so as to expose the heart 

 and lungs, the pericardium slit up and carefully cut away from its 

 attachments, and the lungs inflated by insufflation through the 

 trachea. By keeping up a steady artificial respiration, the move- 

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