l& 2 BIOLOGICAL LECTURES. 



The following conditions point to still more enigmatical con- 

 nections : the disturbance in the development of the brain in 

 congenital defect of both suprarenals, the origin of cretinism 

 and myxoedema after complete extirpation of the thyroid, the 

 default in development of the secondary sexual characters, such 

 as the female habitus, the female mammae, the male habitus, 

 the beard, the male voice after extirpation of the sexual glands ; 

 other cases are unilateral visual atrophy, symmetrical gangrene 

 of the toes and fingers, etc. 



In an extensive series of other cases, primary disturbance or 

 destruction of one part is followed by a compensatory hypertrophy 

 of other parts of the same kind, which take on the function 

 of the disturbed parts. On such manifestations of functional 

 adaptation mainly depends regeneration being insignificant 

 in man the very important principle of the equalization of 

 disturbances after pathological changes, a principle which has 

 of late been thoroughly studied in all its bearings by Noth- 

 nagel (25). 



Of a contrary nature is the enigmatical compensatory hyper- 

 trophy of non-functioning organs, e.g., of the milk-glands of 

 young animals. 



Besides such trophic and functional correlations, many other 

 formative correlations make their appearance during pathologi- 

 cal processes. A mechanical equilibrium of parts under nor- 

 mal conditions is indicated by disturbances like the bending 

 outwards of the teeth when the tongue is abnormally large, 

 the triangular shape assumed by the previously round tibia 

 when the muscles of the leg are developed, and the return to 

 the rounded contour with the atrophy of the muscles in spinal 

 infantile paralysis, the hypertrophy of the interstitial connec- 

 tive tissue following the atrophy of the specific tissues of 

 organs, the proliferation of the pavement epithelium of the 

 outer surface of the body into cavities like those of the nose, 

 mammary glands, ureters, and bladder, which are normally 

 lined with a different epithelium ; or the proliferation of the 

 vaginal epithelium into the uterus. 



To the same category belong the formative reactions to well 

 known external influences, i.e., influences coming from without 



