INANITION OF THYROID IX RATS 313 



there is a distinct tendcnicy to larger folliclc^s in the superficial 

 layers. 



In finer structure, the thyroid at 10 weeks is very similar to 

 that shown at 3 weeks (fig. 2). The height of the follicular 

 cells varies considerably, however. While the maximum is about 

 the same as at 3 weeks, the average (about 8 to 10 micra) is some- 

 what lower. In other words, the cells are usually more flattened, 

 especially toward the perii^hery of the gland. In the larger sur- 

 face follicles, the cells are usually distinctly flattened, 6 micra or 

 less in height. The nuclei in these cells are also correspondingly 

 flattened, their diameters averaging 4 x 6 micra. The nuclei in 

 general are similar to those at 3 weeks in size and structure, usu- 

 ally nearly spherical in form, and averaging about (J micra in 

 diameter. Mitosis is very much less frequent in the cells of 

 the thyroid at 10 weeks than was found in the gland at 3 weeks. 

 While the typical normal structure of the thyroid cells at 10 

 weeks is like that at 3 weeks (fig. 2) , cells of abnormal appear- 

 ance are also found. These atypical forms vary from slight 

 modifications u\) to marked cellular degenerations, and should 

 1)6 carefully noted in order to avoid confusion with the changes 

 during inanition to be described later. 



The flattening of the epithelium in the larger peripheral fol- 

 licles is almost constant, though variable in extent. The flat- 

 tened nuclei are hyperchromatic in type, and often present a 

 more or less deeply-staining, homogeneous background, which 

 may obscure or obliterate the nuclear network and granules. 

 The cytoplasm is reduced in amount, more deeply-staining, and 

 often somewhat homogeneous in appearance. This type of cell 

 occurs so constantly in the peripheral follicles (and occasionally 

 elsewhere) that it can hardly be considered abnormal. I inter- 

 Fig. 5 From a photograph of one lobe of the thyroid ghmd from albino rat 

 No. S 5.10, age f57 days, gross body-weight 22.7 grams (held at maintenance from 

 age of 3 weeks). Gland small, with relative increase of stroma. Parathyroid 

 included. (X 28.) 



Fig. 6 From a photograph of both lobes and a portion of tlie isthmus of the 

 thyroid gland from albino rat No. S 11.64, age 73 days, gross body-weight 24.2 

 grams (held at maintenance from age of 3 weeks) . Follicles larger at periplicry 

 but irregular, many degenerated. Parathyroids relatively large. (X 28.) 



