THE ANATOMY OF THE THYROID GLAND 197 



walls of the venous channels and lymphatic vessels (fig. 14). 

 Thus the relation of the epithelium to the vascular lumen is a 

 very intimate one. 



The cytoplasm of the ''chief" cells is relatively clear, but con- 

 tains a coarsely granular eosinophile reticulum. Some cells 

 appear much more granular than others. In such cells as are filled 

 with colloid, ''colloid cells," the granular reticulum is entirely 

 obscured (fig. 14, A). 



The nuclei of the chief cells are spheroidal, vesicular, and are 

 placed near the base of the cell. From the apices of many of these 

 cells threads of secretion extend to the central colloid mass. The 

 apices of many of the chief cells appear ragged, frayed, and often 

 shrunken, so that the height of the cell is decreased- Such cells 

 present an appearance suggestive of an advanced stage of secre- 

 tion. Other cells contain granules at the distal ends which are 

 arranged in vertical rows, giving this portion of the cell a some- 

 what rodded appearance; such cells are usually well filled with 

 granules. Occasionally a similarly ragged and rodded appearance 

 is seen at the base of the cell and it suggests that secretion may 

 also be discharged at that point. Such a possibility is rendered 

 more probable by the absence of basement membrane and the 

 intimate relation to the lymphatics and blood vessels, these cells 

 often resting directly upon the vascular endothelium. Laterally 

 the epithelial cells frequently are separated from one another, 

 leaving considerable spaces or channels through which secretion 

 may find its way from the follicular lumen to the neighboring 

 vessels; such channels are often occupied in part by colloid and in 

 a few cases I have traced the colloid in a continuous line from the 

 intrafollicular mass to the interior of the vasa and venae lympha- 

 ticae (fig. 10). 



The above observations suggest that secretion may either be 

 discharged from the chief cells into the lumen of the follicle 

 and thence find its way through the follicular wall to the blood 

 and lymphatic vessels, or that it may be discharged from the cells 

 directly into the vessels; this is in harmony with the conditions 

 indicated in the thyroid gland of mammals. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 11, NO. 2. 



