INTERNAL SECRETIONS 



521 



also plays some part in the purin metabolism of the body. In some 

 hibernating animals it also acts as a storehouse of fat. It has long 

 been known to butchers and others that the thymus persists in castrated 

 animals, and atrophies with the onset of puberty in the intact animal. 

 It has been shown, also, that the atrophy is accelerated should the 

 bull be used for breeding purposes or the unspayed heifer become 

 pregnant. It is also suggested that the extirpation of the thymus 

 interferes with the growth of the skeleton. Rickets has been attri- 



Fio. 259. SECTION THROUGH PORTIONS OF PITUITARY BODY OF DOG, SHOWING 

 GLANDULAR AND NERVOUS PORTIONS AND THE PARS INTERMEDIA. (Swale 

 Vincent, drawn by Mrs. Thompson.) 



c, Cleft in glandular portion between glandular portion proper and pars intermedia ; 

 p.g., glandular portion showing three kinds of cells; p.i., pars intermedia; p.n., 

 nervous portion. 



buted to disease of this organ. The evidence in favour of such views 

 is not conclusive. It has recently been stated that tadpoles fed on 

 thyroid became diminutive frogs, while those fed on thymus became 

 giants. 



The Pituitary Body. The pituitary body consists of three portions: 

 (1) The anterior, (2) the intermediary, (3) the posterior lobes. The 

 anterior and intermediary lobes have a common origin from a portion 

 of the glandular epithelium of the sfomodaeum, known as Rathke's 

 pouch. Quite early a differentiation between the two portions takes 



