ATROPHY OF ORGANS WITHOUT APPARENT CAUSE 279 



Moreover, we know that organs may atrophy 

 through correlation with other degenerating organs, 

 or because the whole organism is degenerating 

 although there are no obvious anatomical bonds 

 present between the related parts. As instances of 

 such atrophies we may mention degeneration of the 

 brain resulting on degeneration of the supra-renal 

 capsules ; or of the condition of myxodoema 

 resulting from mechanical or functional disturbance 

 of the thyroid gland. When the essential sexual 

 organs of the male or female are congenitally or 

 accidentally absent, the secondary sexual characters 

 the beard, voice, hair, and whole male or female 

 aspect of the body degenerate. When one eye 

 becomes injured or diseased, a frequent consequence 

 is sympathetic degeneration of the undamaged eye. 



To these cases of correlative atrophy we may 

 add the cases of leaves on many plants with 

 drooping or horizontal branches. On these, the 

 leaves on the upper aspect are frequently rudi- 

 mentary. The appearance is most striking where 

 the leaves are opposite the pairs being at right 

 angles to one another. In a branch of Acer 

 campestre which is upright, all the leaves are of the 

 same size. In a drooping branch the leaves turned 

 towards the sky are small. In plants belonging to 

 very different families (Acanthaceae, Melastomacese 

 Urticacese, etc.) oblique branches exist, and the 

 failure in development of the dorsal upper leaves is 

 invariable. In Procris laevigata (fig. 83) the reduc- 



