col.. 



Fig. 2-14. Endocrine cells from the endoderm and the mesoderm 

 of mammals, (a) Follicle of the thyroid gland, enclosing colloidal 

 store (col.) of secreted diiodotyrosine ; this precursor substance 

 is later reabsorbed by the cells, converted to thyroxine and passed 

 to the blood vessel (b.v.) through the outer cell surface (cf. Figs. 

 4-7 and 4-8). (b) Three kinds of cells in an islet of Langerhans 

 stained with Mallory-azan : a cells that secrete glucagon and have 

 coarse granules that stain red; pale j8 cells that secrete insulin 

 and have fine granules that stain red ; D cells that have no known 

 function and stain blue; b.v., blood vessel, c, capsule of con- 

 nective tissue, (c) Mesodermal cells, forming part of adrenal cor- 

 tex; they are shown in close contact with each other, and with 

 capillaries of the blood supply (cf. Fig. 2-15). The vacuolated 

 cytoplasm (v.c.) is shown after removal of all fat, which is abundant 

 in living cortical cells (after Maximow and Bloom, 1942 and Pauly. 



1957). 



