CIRCULATION. THE HEART. 137 



It was first suggested by Parchappe (1848) ; was chiefly 

 developed by Burdach ; afterwards by Purkinje and Nega 

 (1852); more recently by Malherbe (Nantes) and Fossion ; 

 and admitted by J. Beclard ( Physiologic," 6th ed., 1870). 

 Now, it appears incontestable that the contraction of the 

 papillary muscles transforms the auriculo-ventricular cone, 

 that is, the infundibulum left between the opposite sides 

 of the valves, into a veritable tendinous cord, more or less 

 hollow, between the interstices of which the blood is un- 

 able to make a passage by which it may flow back into the 

 auricle. 1 



What becomes of the blood thus pressed between the 

 sides of the ventricle and the hollow piston which penetrates 

 its cavity ? Under the influence of the contraction of the 

 ventricle and of the working of the auriculo-ventricular sys- 

 tem, which acts as an expulsive apparatus, the cavity of the 

 ventricle has a tendency to completely disappear, even to its 

 base, by means of the fleshy columns (columnae carniae) 

 whose contractions bring the edges of this base in contact 

 with that of the auricular plunging cone. The blood, being 

 unable to return into the auricle, must escape by the arterial 

 orifice of the ventricle (pulmonary artery or aorta). We 

 must, however, observe that these arteries are already, by 

 means of the foregoing contraction, filled with blood sub- 

 jected to considerable pressure, which may be estimated 

 at one-fourth of an atmosphere (see further on). We can 

 easily conceive that, in order to overcome this pressure, great 

 force is required on the part of the ventricle : it therefore 

 contracts slowly and with much force. Contrary to what we 

 have seen in the case of the auricle, the ventricular systole 

 occupies quite an appreciable space of time. It is for this 

 reason, also, that the walls of the ventricles are much thicker 

 than those of the auricles, and in proportion to the resist- 

 ance there is to be overcome, those of the left ventricle being 

 thicker than those of the right. 



Thus the pulmonary artery (or aorta, left ventricle) is 

 forced to receive the blood which the ventricle pours into it. 

 The ventricle is completely emptied: its contraction is no 

 longer necessary, and it is relaxed ; it is now that the heart 

 is still. We represented the total duration of a cardiac rev- 

 olution \>yfive: the first fifth being occupied by the contrac- 



1 This theory has lately furnished a lively discussion in the 

 Academie de Medecine (Gaz. Hebd., 10 Avril, 1874). 



