452 



THE DUCTLESS GLANDS 



(100 to 500 //.), to simulate small cysts. All follicles which possess 

 any considerable lumen contain a peculiar acidophile substance, 

 known as colloid, which is apparently formed by the secretory 

 activity of the glandular epithelium lining the follicles. 



Colloid is a homogeneous or very finely granular substance 

 which stains readily with eosin, taking a very bright tint closely 



b 



FIG. 359. FROM A SECTION OF THE HUMAN THYROID GLAND. 



a, thyroid follicles in transaction ; 6, tangential section of the follicular wall. 

 Hematein and eosin. Photo, x 110. 



resembling that acquired by the hemoglobin of the red blood cells. 

 Frequently, and especially in specimens which have been fixed 

 and hardened in alcohol, it presents a vacuolated appearance. 

 As a rule the lumen of the follicle is not completely filled with 



