THE KINETIC SYSTEM 203 



brain deprived of adrenin does not take the Nissl 

 stain. The consumption of the Nissl substance in the 

 brain-cells is lessened or prevented by morphia, as is 

 the output of adrenin (Fig. 48) ; and the consumption 

 of the Nissl substance is also lessened or prevented by 

 nitrous oxid. Both morphia and nitrous oxid act 

 through their interference with oxidation. We con- 

 clude, therefore, that adrenin can unite with the brain- 

 cells only through the mediation of oxygen. 



In this interrelation of the brain, the thyroid and 

 the adrenals, we have what is, perhaps, the master 

 key to the automatic action of the body ; that is, 

 through the special senses environmental stimuli 

 reach the brain and cause it to liberate energy, which 

 in turn activates certain other organs and tis- 

 sues, among which are the thyroid and the adrenals. 

 The increased output of thyreo-iodin, by facilitating 

 the transmission of electric currents through semi- 

 permeable membranes, increases the passage of nerve 

 impulses and sets the pace for energy conversion. In 

 consequence the adrenals are driven to increased 

 activity, and the increased adrenin in turn excites 

 the brain to still greater activity, as a result of which, 

 again, the entire sympathetic nervous system is acti- 

 vated, as is manifested by the increased heart action, 

 more rapid respiration, raised blood-pressure, increased 

 output of glycogen, increased power of the muscles to 

 metabolize glycogen, etc. 



If the foregoing conclusions be well founded, we 

 should find corroborative evidence in histologic or 

 functional changes in that great storehouse of potential 

 energy and neutralizer of the acid by-products of energy 



