THE ADKENAL GLANDS 85 



differentiate this disease from others showing cer- 

 tain similarities by injecting the hormone into the 

 membrane that lines the eyelid and covers the eye- 

 ball (t'he "conjunctiva") ; after a few minutes there 

 follows a marked dilatation of the pupil ("mid- 

 riasis"), provided the patient has true "dementia 

 precox." 



The amount of adrenaline used in these opera- 

 tions and tests is ridiculously small; perhaps as 

 little as five to ten drops of a solution containing 

 one part of hormone to 1,000 parts of water. 

 Small as such a quantity is, it is yet strikingly 

 effective. What is true of adrenaline seems to be 

 true of all hormones : that their effect is altogether 

 out of proportion to the small amounts of material 

 used. It is this disproportion between amount of 

 material used and the profound changes brought 

 about by such a quantity, that has caused investi- 

 gators to compare hormones with vitamines and 

 enzymes. What connection there is between them 

 remains a mystery. 



Adrenaline in blood. We know that even under 

 normal conditions the blood always contains a 

 small quantity of adrenaline so small, indeed, that 

 it has been estimated at one part in 500 million of 

 blood. For reasons that will soon be apparent, 

 much attention has been given to methods for the 

 quantitative determination of adrenaline. It must 

 be remembered that the quantities involved are 



