746 



J. F. GUDERNATSCH 



f4^^m 



Fig. 4. Sections through the thyroid gland of Salmo irideus. A and B, from a 

 specimen one month old. A, just posterior to the aortic bifurcation; B, near the 

 second branchial arteries. C and D, from a specimen one year old; C, in the aortic 

 bifurcation; D, at the second branchial arteries. 



The follicles are usually circular but there are also irregular 

 forms, due to pressure from the surrounding tissues. The diam- 

 eters of the circular follicles vary between 10 and SOfx, the larger 

 ones being rare. The follicular epithelium is everywhere low, 

 the cells measuring about Sju. The nuclei are all placed with 

 their broad side towards the lumen, which might be called the 

 flat cell position to distinguish it from the cylinder cell position 

 in which the nuclei point towards the lumen. 



Almost all the follicles are filled with clear homogeneus colloid, 

 which has only here and there retracted a little from the wall. Blood 

 capillaries belonging to the follicles, as observed in other species, 



