4 i2 SCIENCE PROGRESS 



secretion of the ductless glands— viz. suprarenal, thyroid, 

 pituitary, thymus. 



(i) The Suprarenal Capsules. 



On slicing through the organ it is seen to be composed of 

 two portions, a central or " medulla," and a peripheral or 

 " cortex." The cortex is the greater in amount, and is in the 

 view of many observers the true suprarenal gland, while the 

 medulla is simply the " paraganglion suprarenale," a portion 

 of the chromaffin tissue which has insinuated itself into the 

 interior of the suprarenal capsule (3). One thing, at any rate, 

 is clear, viz. that we have to deal with two separate and distinct 

 structures. This becomes obvious from a study of the elasmo- 

 branch fishes, where the two portions are separate (4). 



All our knowledge and nearly all our hypotheses in regard 

 to the suprarenal capsule have reference to the " medulla " of 

 the organ. 



(a) Effects of disease. — Destructive disease — usually tuber- 

 culous — of the suprarenal capsules was shown by Addison (5) 

 in 1855 to give rise to a train of symptoms constituting what 

 is now known as Addison's disease. The symptoms are anaemia, 

 profound asthenia, irritability of the stomach, and bronzing of 

 the skin. 



(b) Effects of ablation. — It seems to be generally admitted 

 that the suprarenal capsules are organs essential for life, and 

 that ablation of both capsules is always fatal within a few 

 days (6). But it must be borne in mind that the operation is 

 a very difficult one, and many of the deaths recorded must 

 have been due to causes other than absence of the suprarenal 

 capsules (7). 



(c) General physiological effects of extracts of the suprarenal 

 capsules; Effects of subcutaneous injections. — After sufficiently 

 large doses of suprarenal extract injected subcutaneously we 

 get slowed muscular movements, paresis, and finally paralysis 

 of the limbs (hind limbs always becoming affected first), bleeding 

 from the mouth and nostrils, altered respiration, convulsions, 

 and death. The paralysis is central. The effects are due to 

 the medulla only; the cortex contains no toxic substance. The 

 effects are specific for the suprarenal medulla, and not common 

 to other gland extracts. The toxic material is easily eliminated 

 in some way or other ; this accounts for the large dose required, 



