140 MAN --AN ADAPTIVE MECHANISM 



and the percentage of fatigued and exhausted cells 

 increased. (Fig. 18.) The brain-cell changes wrought} 

 by emotion were identical with those wrought by run- 1 

 ning, by fighting, by infection, by auto-intoxication, ( 

 by physical injury. In intense emotion some cells were' 

 destroyed, their number being proportional to the 

 intensity and duration of the emotion. The cells 

 modified by the emotions, but not destroyed, were 

 restored to the normal state during sleep. 



Having established the histologic evidence that 

 "work" changes are produced in the brain by emotion,^ 

 it is necessary to identify the organs the driving of 

 which exhausts the brain-cells. The two organs whose 

 secretions are known to increase most markedly the 

 activity of the body are the thyroid and the adrenals. 



Relation of the Thyroid to Distance Ceptor Stimulation 



Fortunately a vast number of clinical observations 

 shows a direct relation between the thyroid gland and 

 the emotions. In acute emotions fear, anger and i 

 sexual love the thyroid gland frequently enlarges | 

 and becomes more vascular. 



Beebe as well as Aschoff has shown that electrical stim- 

 ulation of the nerve supply of the thyroid results in a 

 diminution of the iodin content. It is known that the 

 function of the thyroid is dependent upon the presence 

 of iodin in combination with protein in the colloid 

 material of the gland, from which it is probably mobi- 

 lized by activating stimuli. 



Why may this change in iodin content be regarded as 

 evidence that the thyroid is activated by fear ? Because 

 the only proved function of the thyroid is the metab- 



