206 



JEREMIAH S. FERGUSON 



art. thymdextra 



art. thyrsinestm 



19 



Fig. 19. Drawn from a total mount of the thyroid gland of Mustelus canis, 

 showing the course and distribution of the thyroid arteries and the origin of some 

 of the veins of exit. The vessels on or near the ventral surface are indicated by 

 the solid black lines, those on or near the dorsal surface of the gland by dotted 

 lines. 



Fig. 20. A section from the thyroid gland of Carcharias, showing invasion of 

 epithelium and colloid by leucocytes. 



