THE SUPRARENAL CAPSULES OR ADRENALS 



457 



The adrenals are very abundantly supplied with nerves, chkfly com- 

 posed of medullated fibers. These fibers are derived from the solar and 

 renal plexuses and the vagi, but the method of their termination is unknown. 



A vast amount of information has been given concerning the function of 

 the suprarenal capsules within the last 

 few years by the researches of Schafer 

 and Oliver, Zyboulski, Abel, and others. 

 Brown-Sequard, it is true, showed by ex- 

 periment as early as 1856 that removal 

 of the suprarenals is followed by the 

 death of the animal, but his experiments 

 were repeated by others who did not 

 obtain the same results; and it was con- 

 cluded that the suprarenal capsules had 

 no function, or at least that their func- 

 tion was not known. Death was pre- 

 ceded in the case of Brown-Sequard's 

 animals by symptoms somewhat anal- 

 ogous to those of the disease of man 

 known as Addison's disease. The fail- 

 ures to produce symptoms after attempted 

 removal of the glands have probably re- 

 sulted from incomplete removal or the 

 presence of accessory bodies. Accessory 

 suprarenal capsules are commonly present 

 in some animals and are sometimes found 

 in man. Further, if one gland is removed, 

 the other hypertrophies. The experi- 

 ments of all recent observers confirm the 

 original experiments of Brown-Sequard. 

 The presence of the suprarenal capsules 

 is essential to life. 



Schafer and Oliver found that injec- 

 tions of suprarenal extract produced 

 marked effects upon the muscular layer 

 of the arteries, the muscular tissue of the 

 heart, and the skeletal muscles. The 

 muscular layer of the arteries is markedly 

 contracted, causing vaso-constriction and 

 a rise of blood pressure. When the heart is freed from nervous control its 

 contractions are increased both in force and frequency, still further raising 

 blood pressure. If the vagi are undisturbed the heart beats more slowly, 

 showing an increase of vagus tone due to stimulation of the vagus center in 



FIG. 312. Vertical Section of 

 Adrenal. A, Capsule; B, cortex; C, 

 medulla; a, glomerular zone; &, fasci- 

 cular zone; c, reticular zone; v, vein 

 in medulla. (Merkel-Henle.) 



