THE SOURCES OF THE HEART'S ENERGY. 443 



the chemical agencies present becomes converted into mechan- 

 ical energy, which manifests itself as visible motion. 



The left heart the coronaries of which are larger than 

 those of the right presents anatomical features which modify, 

 in a measure, the manner in which its physiological functions 

 are performed. Both its auricle and ventricle containing arte- 

 rial blood fresh from the heart, the Thebesian circulation does 

 not appear to fulfill the primary role it does in the right heart. 

 Indeed, the various experiments of Pratt and his predecessors 

 and our own careful examination of the ox-heart distinctly 

 show that the Thebesian circulation of the left heart, as regards 

 intraventricular orifices, is much less important than that of 

 the right heart. Still, the evident permeability of the inter- 

 ventricular septum and the histology of the left myocardium 

 suggest that the left heart must receive material aid from the 

 adrenal secretion and its granules ft. This feature will again 

 be referred to in the twelfth chapter. 



A feature that may be considered as demonstrated, and 

 common to both sides, is the return of the blood, whether its 

 source be the Thebesian or coronary systems, by way of the 

 coronary veins. We have seen that Langer expressed the opin- 

 ion "that the foramina Thebesii in the ventricles communicate 

 with the veins by capillaries alone." Our conception of the 

 process involved would necessitate such an arrangement as re- 

 gards the right heart. Indeed, so direct is this connection that 

 even such viscid substances as starch and celloidin were found 

 by Pratt, when introduced into the coronary veins of the ox, 

 to emerge from the foramina Thebesii. Still, we could hardly 

 expect such a free transit on the left side of the organ, inas- 

 much as the presence here of arterial blood only would suggest 

 the presence of a structural organization similar to that of ordi- 

 nary muscles. Indeed, referring to the vascular connections 

 of the left heart, Pratt says: "So intimate a connection, how- 

 ever, between the coronary veins and the vessels entering the 

 left ventricle I have not yet been able to demonstrate." Again, 

 on the right side the connection with coronary veins must evi- 

 dently be a physiological one, since "a small, but steady, stream 

 of venous blood issued from them" when the veins were incised 

 after the right ventricle had been filled with defibrinated blood. 



