82 MEDULLA 



solution, the oxidation products formed still reduce phospho- 

 tungstic acid. Folin's method is also inapplicable in the 

 presence of cocaine or procaine. The use of the Folin-Denis 

 colorimetric method can not therefore be relied upon as a test 

 for the presence of epinephrine. Thus extracts of the cortex 

 often show the apparent presence of as much as a milligram of 

 epinephrine per gram of tissue when biological assay reveals 

 the absence of any epinephrine. 



Other less important color reactions are also given by epineph- 

 rine and have been suggested for its determination. Thus 

 it gives a permanent red color with CuS0 4 and KCN. The 

 Frankel-Allers color reaction depends on the formation of a 

 rose-color when epinephrine hydrochloride is heated with KI0 3 

 and dilute H 3 P0 4 . Seidell suggested the use of the red color 

 produced on oxidizing epinephrine with Mn0 2 . 639 



Whitehorn 675 has recently described a method for the deter- 

 mination of epinephrine in biological fluids which depends 

 upon its adsorption by silica. The adsorbed epinephrine is 

 eluted by sulfuric acid and determined colorimetrically. The 

 method is sensitive to one part of epinephrine in 50 million 

 parts of solution. 



As may be seen from the preceding comments the colorimet- 

 ric determination of epinephrine, despite its simplicity and 

 accuracy in pure solution, is fraught with errors in most condi- 

 tions in which it is desired to be applied. Careful check by one 

 of the biological methods, to be described in Chapter VI, is 

 thus always necessary 601 - 659 if one is to obtain reliable results. 



THE ORIGIN OF EPINEPHRINE IN THE BODY 



The origin of epinephrine in the body is still unproven al- 

 though several suggestions have been offered to account for 

 its probable origin. The close structural relation which epi- 

 nephrine bears to the two amino acids, tyrosine and phenyla- 

 lanine, suggests that either might give rise to epinephrine by 



