1330 PHYSIOLOGY 



herbivora respectively. Forsyth has shown that, in man, the situation 

 of the parathyroids corresponds almost exactly with the places in which 

 are found occasionally accessory thyroids ; and, according to Edmunds, 

 after excision of the thyroid, the parathyroids undergo histological 

 alteration and are converted into thyroid tissue, the cells taking on an 

 alveolar arrangement and producing colloid material. According to 

 this view the parathyroids would represent simply immature thyroid 

 tissue. On the other hand, it has been suggested (Biedl) that the para- 

 thyroids have a function entirely distinct from that of the thyroid 



_ .. . pio* 



'" *@ & ''"'" / 

 \ A ^s* , / /^p* 



4^^-P 



fTZOi 



"'' 



FIG. 546. Section of parathyroid. (KoHN.) 



ep, secreting epithelium ; pig, cells containing pigment ; czp, sinus-like 

 capillaries ; end, endothelial cells. 



gland, removal of the thyroids producing simply a condition of 

 cachexia and the changes associated with myxcedema, while removal 

 of the parathyroids is responsible for the nervous disturbances and 

 tetany observed after total extirpation of these organs. The matter 

 cannot yet be regarded as definitely settled. 



THE PITUITARY BODY 



The pituitary body consists of two parts which have separate 

 modes of origin. An outgrowth from the buccal cavity in the embryo 

 meets a hollow extension of the anterior cerebral vesicle. The buccal 

 ectoderm gives rise to the anterior lobe and pars intermedia of the 



