THE ADRENAL SECRETION AND THE HEART. 431 



plasma into their smaller ramifications and finally into the 

 veins. The larger channels carry the corpuscular elements to 

 the latter. The role of the coronary arteries will be referred 

 to later on. 



The right heart, as we view the process, owes its functional 

 activity mainly to the suprarenal secretion brought to the 

 cavities by the vena cava. We have sufficiently emphasized 

 the power of this agent to restore cardiac action and sustain 

 it even when the entire spinal cord has been obliterated. The 

 manner in which it exercises its powers is similar to that of 

 the arterial blood on the left side. On penetrating the auricle 

 the contractile structures are submitted to its immediate ef- 

 fects; but the orifices of the Thebesian vessels or channels are 

 more numerous and larger than in the left auricle. The mem- 

 branous edges previously referred to as valves by the investi- 

 gators quoted do not appear to us to merit being considered 

 as such after careful examination of these structures in the 

 ox-heart. The aperture being closed by the least squeezing of 

 the tissues containing them, it seems evident that they should 

 as readily close under the powerful contraction of the auric- 

 ular tissues. The right ventricle also presents a very much 

 larger number of Thebesian orifices than the left, while its 

 walls, though thinner, plainly show the ramifications of these 

 channels. That the venous blood charged with suprarenal se- 

 cretion should at once penetrate the latter when the ventricle 

 begins to contract is self-evident. Return of the blood to the 

 circulation is effected in the same way as in the case of the 

 left heart: i.e., through the coronary veins. 



The whole process is an exceedingly uncomplicated one, 

 but, as we will see later on, it simplifies many obscure prob- 

 lems, while affording, in connection with the coronary arterial 

 blood, a supply in keeping with the vital importance of the 

 organ itself. Again, Dr. Pratt' s experiment, in which blood 

 injected into the left auricle flowed freely from the right ven- 

 tricle, emphasized the possibility of compensation in case of 

 need. Thus, while under normal conditions, the pressure in 

 both ventricles must be equal, reduced contraction of the 

 right ventricle, for example through insufficiency of the ad- 

 renals would automatically cause the arrival into it, through 



