The various extracts that have been used in these experiments were 

 mixtures of unknown substances, and it is as yet an unsolved question 

 whether the various actions at present ascribed to the gland are due 

 to one and the same substance. 



We are at present interested in the isolation of the blood-pressure- 

 raising constituent, for in a purified state, separated from all other 

 constituents, it might become a therapeutic agent of great importance. 



On the chemical side but little advance has been made over Vul- 

 pian's* striking original contribution more than forty years ago. Vul- 

 pian observed that the juice expressed from the suprarenal capsule 

 of many different animals behaved in a striking manner toward ferric 

 chloride and toward solutions of iodine, giving with the former rea- 

 gent an emerald green color, and Avith the latter a beautiful rose 

 carmine tint. No other tissue of the body, so far as investigated by Vul- 

 pian, gave these reactions. 



Virchowf substantiated Vulpian's statements, but added nothing 

 new. A year after Vulpian's first announcement his second paper ap- 

 peared in conjunction with Cloez,:}; verifying and extending his first 

 observations and stating his failure to isolate the chromogenic sub- 

 stance or substances to which the above reactions are due. 



Equally unsuccessful were Arnold§ and Holm.|| Krukenberg,** 

 years after, repeated the work of Arnold and came to the conclusion 

 that the chromogen of the suprarenal capsule is a non-volatile, nitro- 

 genous and ferruginous organic acid which is probably related to the 

 turacin of the musophagidae and to chlorophyll. He assumed that the 

 substance giving the green color with ferric chloride is not the chromo- 

 genic substance of Vulpian, but more likely pyrocatechin accompany- 

 ing the chromogen. Attention being thus attracted to the possible 

 occurrence of pyrocatechin in the suprarenal capsule, others took up 

 the subject. 



Brunnerj-f found that an alcoholic extract can be made to give 

 nearly all of the reactions of pyrocatechin; thus, it gives the well- 

 known green color with ferric chloride, passing into a fine red on the 



* Note sur quelques reactions propres i la substance des capsules surr^nales, 

 Compt. rend, xliii (1856), 663-665. 



fVirchow's Archiv, xii (1857), 481-483. 

 + Compt. rend., xlv (1857), 340-343. 

 §Virchow's Archiv, xxxv (1866), 64-107. 



Journ. f. prakt. Chemie, c (1867), 150. 

 ** Virchow's Archiv, ci (1885), 542-591. 

 -|-f Schweizer. Wochenschr. f. Pharmacie, xxx (1892), 121-123. 



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