430 THE DYNAMICS OF CARDIAC ACTION. 



All these features seem to fully supply the needs of the 

 function with which the secretion of the suprarenal glands 

 must be connected, if the phenomena witnessed in many dis- 

 orders and after the use of most remedies have been correctly 

 interpreted. That we are in the presence of a dual process 

 of which the suprarenal secretion, operating in the right heart, 

 and the arterialized blood in the left heart are active factors 

 seems probable. Again, the marked power of arterial blood 

 or rather of plasma since the defibrinated blood filtered 

 through cotton was used to sustain functional activity, even 

 when only poured into the ventricles, as shown by Pratt, cer- 

 tainly indicates that the blood must alone be able, during 

 life, to compensate, in case of need, for insufficiency of blood 

 furnished by the coronary arteries. 



The contractions of the left heart seem to us to be greatly 

 assisted by the arterial blood that enters it, and mainly by 

 that which enters the cavities themselves. The experiments 

 of Pratt having shown that contraction could be produced by 

 contact with arterialized blood, the arrival into the auricle of 

 a normal quantity of this fluid must be fully capable, there- 

 fore, of causing contraction of the walls of that cavity. The 

 relations of the several structures and the mechanism involved 

 seems to us to be as follows: The main structures upon which 

 the arterial blood reacts are (1) the musculi pectinati and (2) 

 the sinus venosus and appendix auriculae, all of which are so 

 disposed as to offer as much surface as possible to the blood. 

 The walls of the cavities mentioned are provided with numer- 

 ous channels, the Thebesian "veins/' to satisfy this purpose. 

 The blood which enters the auricle when it is dilated pene- 

 trates all the circuitous areas around the musculi pectinati and 

 into the Thebesian vessels, and the ensuing contraction forces 

 the blood-plasma into the smaller subdivisions of these vessels, 

 from which they find their way into the auricular veins. When 

 the arterial blood reaches the ventricle, a process similar to the 

 preceding occurs. The columns carneas are disposed so as to 

 offer considerable surface to the blood, while the ventricular 

 walls are permeated with Thebesian channels, into which the 

 blood penetrates during diastole. The contraction induced 

 closes the apertures of these channels, and forces the blood- 



