134 The Endocrine Organs 



of the skeleton, are not seen. In such animals as birds and deer, in which 

 the external characteristics of the male sex are well marked, these 

 characteristics fail to show themselves, the general features of development 

 approaching those usual to the female sex. In the skeleton, the epiphyses 

 long remain separate ; the limb bones are longer and more delicate than 

 usual, and the sutures of the skull slower in ossifying. The mental char- 

 acter also tends to retain a more infantile type. Most of the ductless 

 glands are in some way affected, the growth of the thyroid being 

 diminished, that of the suprarenal cortex, pituitary, and thymus increased : 

 the last-named organ shows arrest of its normal retrogressive changes. 



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FIG. 92. Interstitial cells of testicle, cat. Magnified 200 diameters. Parts of three 

 tubules are included in the photograph. 



If castration is performed in the mature animal, and therefore after the 

 secondary sexual characters have become developed, there may be some 

 retrogression of these, and such accessory generative glands as the prostate 

 tend to undergo atrophic changes. But the effects are now mainly upon 

 metabolism, and are shown in a tendency to increased formation of fat, 

 although the limit of assimilation of carbohydrates is lowered and alimentary 

 glycosuria is more easily produced. How far these effects on metabolism 

 are direct or how far indirect, through other endocrine organs, it is not pos- 

 sible to say, but the fact seems to be well established that the pituitary body 

 becomes hypertrophied after castration (Fichera, Cimorini). The increased 

 length of limb bones which occurs when the operation is performed before 

 adolescence may be associated with this change in the pituitary (Tandler). 



In certain animals which undergo seasonal variations in sexual activity the 

 secondary sexual characters which generally accompany these variations are 

 also abolished or modified by castration. Thus if a stag is castrated, the antlers 



