444 INANITION AND MALNUTRITION 



usually occur on the human diets in England. Bayard ('23) and Olin ('24) 

 support the theory of iodin deficiency as the cause of endemic goiter. 



Although oxygen is not, strictly speaking, a nutritional factor, it is of interest 

 in this connection to note that Martin, Loewenhart and Bunting ('18) found 

 thyroid hyperplasia, with hydropic and hyalin degeneration of the cells in 

 rabbits, as a result of decreased oxidation. 



Vitamin Deficiencies. — In infantile beriberi, Andrews ('12) found but 

 slight changes in the thyroid gland, aside from congestion. 



In pigeons with experimental beriberi, Funk and Douglas ('14) noted definite 

 "signs of degeneration" in the thyroid and other glands. Douglas ('15) 

 described great individual variations in the thyroid of normal pigeons, as well 

 as in those on polished rice diet, producing beriberi. In extreme stages, the 

 follicles may be partly or wholly disintegrated. The variations apparently 

 depend in part upon the general condition of nutrition. Drummond ('18) 

 observed very small thyroid glands in some young rats (black variety of Mas 

 norvegicus) greatly emaciated at death on a diet deficient in vitamin B. 



McCarrison ('19, '20, '21) found that in polyneuritic (beriberi) pigeons the 

 thyroid gland undergoes a moderate atrophy, the decrease in weight being less 

 than during total inanition (Fig. 35). Like Douglas, he found marked varia- 

 tions in the histological structure, even in normal pigeons. He ('21) concluded: 

 "Excluding, then, infective processes, which so constantly reveal their presence 

 in the body by initiating pathological changes in the thyroid gland, I find this 

 organ, so far as can be judged by histological study, to be amongst the least 

 affected of all organs by the deficient dietary. The changes which are attrib- 

 utable to this cause consist in mild or moderate degrees of congestion and in 

 necrobiosis of a relatively small proportion of the secretory cells. Confusion as 

 to the changes directly attributable to the dietetic deficiency is apt to occur 

 unless complicating infections are excluded. It is to these that pronounced 

 congestion, necrosis, and denudation of the alveolar epithelium are directly due 

 and not, as I had previously concluded, to the dietetic deficiency; although such 

 deficiency is indirectly responsible for them, since it renders the thyroid very 

 liable to attack from bacterial agencies." Similar changes were observed in 

 the thyroid gland of monkeys and guinea pigs on variously deficient diets. 



Brucco ('20) concluded that in dogs on a polished rice diet, the thyroid 

 (like the suprarenal), after a transient stage of hyperf unction, undergoes 

 degeneration. In young rats on a vitamin-free (polished rice) diet, Tsuji 

 ('20) noted thyroid atrophy, with secondary changes in other organs, ascribed 

 to hypothyroidism. 



In pigeons and fowls on a polished rice diet, Findlay ('21) found but slight 

 decrease in weight of the thyroid gland, similar to that during inanition (Table 

 13). The gland appears anemic. Histologically the structure may remain 

 normal, or the follicular epithelium may be degenerated. Souba ('23) noted 

 that in young chickens on diets deficient in vitamin B there is a slight loss in 

 thyroid weight, somewhat proportional to the loss in body weight. In adult 

 pigeons on a vitamin-free diet, Lopez -Lomba ('23) found the thyroid weight 



