198 



JEREMIAH S. FERGUSON 



Fig. 14. A, section of the thyroid gland of Mustelus showing a follicle com- 

 pletely surrounded by "colloid cells." At y a carmine granule, derived from the 

 injection mass, lies in the vena lymphatica. B, section of the thyroid gland 

 of Mustelus showing follicles lined entirely by "chief cells." 



