CHAPTEE IX. 



THE ADRENAL AND VAGAL SYSTEMS IN 



THEIR RELATIONS TO CARDIAC AND 



PULMONARY FUNCTIONS. 



WE have repeatedly referred to the functional connection 

 between the secretion of the adrenals and the heart. Is this 

 connection direct or is it indirect? In other words, is it the 

 result of a direct stimulation of the heart-muscle such as is 

 produced by suprarenal extract, or of the stimulating effect 

 to which the increase of oxidizing processes, including those 

 of the cardiac cerebro-spinal centers, give rise? Analysis of 

 this question tends to show that both processes prevail simul- 

 taneously when from any cause the adrenals become over- 

 active. 



THE ADRENAL SECRETION AS THE SOURCE OF THE FUNC- 

 TIONAL ACTIVITY OF THE RIGHT HEART. 



As freshly-oxidized blood is constantly being supplied to 

 loth sides of the heart, the specific action of digitalis upon 

 the right heart to which we have referred cannot be ascribed 

 to the oxidizing substance. Again, it would seem that the 

 suprarenal secretion itself could hardly be credited with a 

 local stimulating action upon the cardiac walls when the thick- 

 ness of the myocardium is recalled, unless the latter be pro- 

 vided with channels calculated to insure the penetration of 

 the secretion to its deeper tissues. Not only do such chan- 

 nels exist, however, but they are so disposed as to enable the 

 adrenal active principle to permeate the entire myocardium 

 and be equally distributed among the contractile elements. 

 The channels to which we ascribe such important functions 

 have been known as the "foramina of Thebesius." 



These canals are described in Gray's "Anatomy" as fol- 

 lows: "The foramina Thebesii are numerous minute apertures, 

 the mouths of small veins (venas cardis minimae), which open 

 on various parts of the inner surface of the auricle. They 

 return the blood directly from the muscular substance of the 



(421) 



