564 



THE DUCTLESS GLANDS ENDOCRIN GLANDS 



which capillary vessels are here and there found, the larger blood-vessels 

 occupying the coarser bands of the fibrous stroma. In such glands the 

 two cell varieties are either intermingled irregularly, or the acidophil 

 cells may occur in scattered groups which are interspersed among the 

 more numerous principal cells. 



In certain instances the epithelial cells are arranged in small alveo- 



FIG. 486. HUMAN PARATHYROID TISSUE, MODERATELY MAGNIFIED. 



Several blood-vessels are included. Capillary vessels can scarcely be recognized 

 with this magnification. Hematein and eosin. Photo. X 300. 



lar groups which are surrounded by a network of capillary vessels. This 

 arrangement appears to be more frequent in young individuals. The 

 cell groups in this type of gland frequently form branching columns. 



Occasionally, epithelial cells surround a central lumen, in which are 

 small masses of an acidophil substance which resembles colloid in its 

 reactions. This colloidal material is less abundant in the human para- 



