THE AUTONOMIC NERVOUS SYSTEM 203 



fluences in time of stress the thyroid shows augmented secretory 

 activity. The organ is innervated by the thoracico-lumbar system, 

 and so may be excited directly. In addition to this means of 

 arousing it, the thyroid may be stimulated to activity chemically 

 by means of adrenin. Whenever the blood is charged with this 

 latter hormone the thyroid is thrown into activity. So far as we 

 are able to judge from present knowledge the importance of this 

 emergency action of the thyroid is in the general speeding up of the 

 chemical activities of the Body; and possibly also in heightening 

 nervous irritability, although that the latter effect can be brought 

 about so promptly as would be necessary in an emergency 

 mechanism has not been demonstrated. 



