3()() C. M. JACKSON 



the length and character of the manition. In acute inanition of 

 adult rats, with loss of about one-third in body weight, the thy- 

 roid gland had apparen cly lost but little if any in absolute weight ; 

 in chronic inanition of adults, the average apparent loss of the 

 thyroid was about 22 per cent; while in young rats held at main- 

 tenance (constant body weight) by iniderfeeding for se\'eral 

 weeks the average loss was about 24 per cent. In order to de- 

 termine what histological changes are correlated with these 

 changes in gross weight, material was preserved for further 

 study. On account of its intimate association with the thyroid, 

 the jiarathyroid gland was also included in this investigation. 

 The results are presented in the present paper, which is the third 

 of a series of studies upon the effects of inanition. The work is 

 being carried on with the assistance of a special grant from the 

 research fund of the (Graduate School of the University of Min- 

 nesota. 



MATERIAL AND METHODS 



The material used included the thyroid (and included para- 

 thyroid) glands of the albino rat (Mus norvegicus albinus) from 

 previous studies (Jackson '15a, 'lob), together with some col- 

 lected since. In all, more than 50 normal glands were sectioned 

 and studied, A'arying in age from newborn to adult (15 months). 

 These were chiefly controls from the same litters as those used 

 for experiments (including several controls used in experiments 

 by E. R. Hoskins and C. A. Stewart). In addition, I am in- 

 debted to Professor Bensley and Mr. Burgett, of the University 

 of ( 'hicago. Professor Addison, of the University of Pennsylvania, 

 and Professor p]\'ans, of the University of ("alifornia, for mate- 

 rial kindly furnished in order to investigate possible local varia- 

 tions in normal thyroid structure of the rat. 



Of the animals subjected to inanition, the thyroid and para- 

 thyroid were obtained from 14 of the younger rats held at main- 

 tenance for various periods (chiefly beginning at 3 weeks and 

 ending at 10 weeks of age). Of the adult rats, glands were 



