136 THE DUCTLESS GLANDS 



for pigment becomes developed in large amount in ganglion 

 cells only during the process of degeneration. 1 Wieting and 

 Hamdi, discussing melanin-pigmentation, regard the formation 

 of pigment as a protective arrangement e.g., it is laid down 

 in the skin to protect the underlying structures. Solger looks 

 upon the skin pigment as a protective against ultra-violet light. 



The pigments of the body (respiratory, biliary, urinary, 

 melanins, lipochromes, etc.) may be divided into (1) iron- 

 containing pigments ; and (2) fat-containing pigments. The 

 second group includes the degeneration pigments, the lipo- 

 chromes, and the melanins. The pigment in Addison's disease 

 appears to belong to the melanins. 



There are various theories as to the mode of formation of 

 the pigment. It has been suggested that it arises as a result 

 of over-activity of the cells of the stratum Malpighii, due to 

 increased nervous stimulation, the result of mechanical irrita- 

 tion of the nerves round the adrenals. Eiselt believes that in 

 consequence of the failure of the antitoxic adrenal function 

 (of the cortex) the accumulated products act autolytically 

 upon the protein. Then, by the action of tyrosinase upon the 

 aromatic molecular complexes thus formed, there arises an 

 accumulation of melanin. 



A modification of this theory, but involving the hypothesis 

 that the medulla is concerned in the pigmentation, based upon 

 the work of v. Fiirth and Halle has been put forward by Adami. 

 The melanin appears to be formed by the action of oxidases 

 upon tyrosin and other aromatic products of protein decom- 

 position. It seems possible that adrenin is manufactured in a 

 similar kind of way, so that when the adrenal bodies are 

 diseased the tyrosin and allied bodies accumulate in the tissues, 

 and the greater darkening of the superficial parts most exposed 

 to light and air gains its explanation from the more active 

 oxidation of those aromatic bodies in these regions. 



Pathologists have never until quite recently given due 

 consideration to the essential difference between the cortex 

 and medulla of the adrenals. We have seen that these repre- 

 sent two separate and distinct kinds of tissue, which only come 

 into relation with each other in the higher vertebrates, and 



1 There seems no reason why this pigmentation in degenerating nerve cells 

 should not be an example of a protective effort (albeit ineffective) on the part 

 of the cell. 



