DUCTLESS GLANDS AND NERVOUS SYSTEM 2J 



Let us examine more closely the action of these hormones or ductless 

 glandular extracts in this direction. 



Of adrenalin, the internal secretion of the chromamn tissue, we have al- 

 ready mentioned that it is of great significance for the excitability of the 

 myoneural junctions. As in a genetic relationship the chromamn tissue be- 

 longs to the sympathetic system, this system possesses within itself a regu- 

 lator of its excitability (Bayliss and Starling). As for the physiological 

 significance of the chromaffin tissue, it must furthermore be considered that 

 by the lasting function of this tissue there is maintained a certain dis- 

 tribution of blood. The sympathetic innervation of the different vascular 

 districts is of different richness; for example, the vessels of the muscles and 

 skin are very abundantly supplied, while the vessels of the lungs, of the 

 coronary arteries, and of the brain possess a weak sympathetic supply. 

 Priestley and 7 have pointed out that the venous blood emanating from the 

 organs with a rich sympathetic innervation are adrenalin-free or are es- 

 sentially poorer in adrenalin than the arterial blood flowing to them. The 

 liver is supplied with blood rich in adrenalin only by the hepatic arteries, 

 while the very much larger amount of blood that flows to it through the portal 

 vein is adrenalin-free or at least poor in adrenalin, as this blood has already 

 passed through the capillary system of the intestine. Hence in a quiet 

 fasting organism there occurs a definite blood distribution, a distribution 

 that may be regarded as purposeful. Thus the resting organs (muscle, 

 skin, intestine, etc.) contain very little blood, while those organs whose 

 activity is necessary for the maintenance of life (heart, central nervous 

 system, lungs, liver, etc.) are relatively rich in blood. The former become 

 supplied with more abundant blood, through the regulatory activity of the 

 sympathetic simultaneously with increased cardiac activity, only when they 

 are functionally more in demand. 



The chromaffin system plays an important role in the regulation of the 

 blood's plasma contents. After the injection of large amounts of adrenalin, 

 Bertelli, Schweeger and 7 saw an appreciable increase in the count of the red 

 cells of the circulating blood. As this hyperglobulia survives the vaso-con- 

 traction for a long time, the cause of this is to be sought not only in the press- 

 ing-out of the plasma, but also in an alteration of the permeability of the ves- 

 sel wall on account of which the return flow of plasma is delayed for a long 

 time. Now it is known that in individuals who are brought relatively rapidly 

 into an atmosphere poor in oxygen (mountains, balloon trips, etc.) the num- 

 ber of red blood cells increases very rapidly. The hyperglobulia brings about 

 greater respiratory surface, this counterbalancing the slighter partial pressure 

 of the oxygen. To-day it is generally assumed that at least in rapid transi- 

 tions it is not the result of the increased production of erythrocytes. We 

 believe rather that it is due chiefly to a regulatory exudation of plasma into 

 the tissues, and that in this regulation is involved the chromaffin tissue. 



