544 PHYSICAL EXAMINATION OF THE CIRCULATORY ORGANS. 



with the blood contained in the cavities, and the action of the 

 muscular structure on this. The phenomena connected with 

 the action of the heart are in the majority of instances quite 

 distinctive and capable of appreciation, while, for the intelli- 

 gent comprehension of the changes connected Avith that action 

 in disease, the more salient points connected with it ought to 

 be borne in mind. 



The contraction of the auricles is simultaneous ; the con- 

 traction of the right and left ventricle succeeds that of the 

 auricles, and is synchronous. 



The muscular fibres of each j)art relax immediately follow- 

 ing their contraction, and a distinct period of repose intervenes 

 between the contraction of the ventricles and secondary con- 

 traction of the auricles. Thus, if we start with this interval of 

 repose, the general cardiac diastole, we find that the two 

 pouches are being filled with blood from the great venous 

 trunks. When sufliciently full, the auricles contract and send 

 a portion of the blood they contain into the ventricles, and 

 these, immediately contracting, send the blood into the arterial 

 tubes. This passage of blood into arteries is a necessary con- 

 sequence of the contraction of the ventricles, for with their 

 contraction is the raising of the auriculo-ventricular valves 

 which prevent the return of the blood into the auricles ; the 

 blood is thus forced into the arterial openings, the valves of 

 which are opened by the impulse of the liquid. When the 

 heart returns to a state of repose the blood is prevented from 

 returning to the ventricular cavities by the dropping of the 

 uphfted valves. 



By the term systole is meant the contraction of the Avails of 

 the heart's cavities ; by diastole, the respose or relaxation of 

 the same. 



It is thus that each complete revolution of the heart, or 

 entire performance of its circle of function or action, is indicated 

 by two successive sounds, betAvecn Avhich are two intervals of 

 repose. The sounds are unlike, and the mtervals of silence 

 vary in duration. 



The first or systolic sound is prolonged as compared Avith 

 the second, and of a dull character, and is immediately suc- 

 ceeded by a very short interval of silence, folloAvcd by the 

 diastole or second sound, short and sharp, foUoAv^ed by a more 



