SECRETION OF THE DUCTLESS GLANDS. 875 



Physiology of the Medulla. The Active Principle, Epinephrin. 

 Chemical investigations of the substance in the medulla which 

 causes the inhibition of the heart and the rise of blood-pressure 

 have been very successful. The substance has been prepared in 

 pure form, its chemical structure is known, and it has been made 

 synthetically outside the body.* The credit for the most impor- 

 tant initial work is due to Abel, while the final isolation in pure form 

 as crystals was accomplished by Takamine and independently by 

 Aldrich. The last-named observer determined the correct formula 

 for the active substance, namely, CgHiaNOs, and later workers 

 (Stolz and Dakin) succeeded in demonstrating its chemical struc- 

 ture as a dioxyphenyl ethylol-methylamin, C 6 H 3 (OH) 2 CHOH- 

 CH 2 NHCH 3 . The presence of the oxyphenyl group in the com- 

 pound would suggest that in the body it is probably derived from 

 ty rosin. This active substance is designated in the literature 

 under a variety of names, those commonly used being epinephrin 

 and adrenalin. It is a basic body which gives a number of char- 

 acteristic color reactions, and in alkaline solutions is readily oxi- 

 dized to a substance that fails to exhibit the characteristic epineph- 

 rin reaction on heart-rate and blood-pressure. 



Distribution of the Epinephrin. The Chromaffin Tissues. As 

 stated above, the epinephrin occurs in the adrenal gland in the cells 

 of the medulla, but not in those of the cortex. When the medullary 

 cells are treated with chromates they give a characteristic yellow 

 or brown reaction, which is spoken of as a chromaffin reaction and 

 has been used to locate similar cells in other tissues. It would seem 

 that cells of this variety may be found generally or frequently in 

 the sympathetic ganglia, so that it has been suggested that primi- 

 tively each such ganglion contained two varieties of cells, the nerve 

 cell or ganglion cell and the chromaffin or paraganglion (Elliott) 

 cell. Clumps or strings of such cells occur also along the course of 

 the abdominal aorta below the level of the adrenal glands, and, as 

 was stated above, in some of the fishes the medullary cells of the 

 adrenal gland are separated anatomically from the cortical cells. 

 On account of the color reaction and the demonstration, in some 

 cases at least, that this color reaction indicates the presence of 

 epinephrin, it has become customary to group all the cells exhibit- 

 ing the chromate reaction under the general term of chromaffin 

 system^ and to suppose that all this tissue, wherever found, has a 

 common physiological significance. The medulla of the adrenal 

 gland is the most conspicuous and important group of these cells, 

 but it is assumed that in case of removal by disease or experiment 



* For description of chemistry and references, see Barger, "The Simpler 

 Natural Bases" (Monographs on Biochemistry), 1914. 



t See Vincent, "Proceedings of the Royal Society," B, 82, 502, 1910. 



