316 



C. M. JACKSON 



In size, the epithelial cells of the thyroid follicles in the young 

 rats held at maintenance are \'ariable but distinctly smaller than 

 normal. E\'en the largest cells found rarely reach the average 



Fig, 7 A portion of the same thyroid gland shown in figure 4 (rat No. 11.63, 

 niainfenance from 21 to 72 days of age), magnified to show details of histological 

 structure. The area represented shows the hypochromatic (incipient karyo- 

 lytic) type of nuclear structure, which is relatively infrecjucnt. Cells reduced in 

 average height (cf. fig. 2). Cytoplasm reduced in amount nnd vacuolated in 

 structure. Stroma here normal. (X 750.) 



