EFFECTS ON THE THYROID AND PARATHYROID GLANDS 



441 



Hibernation. — Peiser ('06) concluded that the secretory activity of the 

 thyroid gland in bats decreases during hibernation. The follicular epithelium 

 was found flattened, "colloid cells" lacking, and the colloid reduced to a small 

 amount. A hedgehog killed in February also showed no colloid in the thyroid 

 follicles. 



Adler ('14) likewise observed an atrophy of the thyroid gland with a dis- 

 appearance of follicular colloid in hibernating bats, and concluded that the 

 decreased thyroid secretion might cause the phenomena of hibernation. Adler 





mm 



y 



Fig. 114. — A portion of a section of the thyroid gland in an albino rat (11.64) held at 

 constant body weight by underfeeding from 3 to 10 weeks of age. This area shows advanced 

 stages of follicular degeneration, with cells in various stages of degeneration and disintegration. 

 There is a .tendency to desquamation of the epithelium, with destruction of the colloid and 

 obliteration of the follicular lumen. Some of the nuclei appear karyolytic, although karyopyc- 

 nosis predominates and karyorrhexis frequently appears. X750. Technique, etc. as in Fig. 

 113, which is to be compared. (Jackson '16.) 



('20) described various grades of atrophic regressive changes in the thyroid 

 follicles of hibernating bats, involving in extreme cases a complete destruction 

 of the follicles. Upon the awakening in the spring, new follicles develop from 

 the remaining interfollicular cell-masses. In hibernating hedgehogs, similar 

 but less marked changes were found. 



