INFLUENCE OF DIET AND IODIDES OPOSSUMS 59 



Since the amount of colloid stored in the follicles of the gland 

 varies within wide limits, even in normal glands, it was desirable 

 to ascertain as nearly as possible the net weight of the gland 

 tissue. This was accomplished, roughly, by drawing projected 

 sections of the glands, cutting out the colloid areas, and weigh- 

 ing. The error in this method is, of course, considerable, but 

 not nearlj^ so great as the error introduced by neglecting the 

 weight of the colloid itself in comparing the relative weights of 

 animals and glands under experimental conditions. The un- 

 fortunate lack of any data on the normal curve of growth for these 

 animals, such as those collected by Donaldson, Hatai and Jack- 

 son for the rat, increased the difficulty of comparison, but 

 fortunately the differences obtained were for the most part of 

 such magnitude, that little doubt remained of the nature of the 

 changes in the experimental glands and of its direction, particu- 

 \sLT\y in view of the fact that the histological examination of the 

 gland confirmed the conclusions based on weight. 



In the tables which follow the computation of the ratio of the 

 gland weight — body weight has been made on the basis of the 

 initial weight of the animal when received, since the fluctuations 

 of weight were so great in some of the experiments, and since the 

 experiments lasted too short a period in the majority of cases to 

 allow for much natural growth. 



Animals which were receiving iodides were placed in a special 

 room in the basement, the rest of the colony in a room on the 

 fifth floor, to avoid complicating the experiments by iodine in 

 the atmosphere. 



Table 1 includes the controls of the four succeeding series, 

 that is, animals kept on an unrestricted diet of table scraps for 

 different periods of time as indicated. 



The magnitude of the increase in the weights of these glands 

 will be better understood by comparing them with those of ani- 

 mals of similar weight in series four. Histologically all of these 

 glands showed a high degree of hyperplasia, associated with re- 

 duction of the colloid in the follicles. 



Number five which in the table shows a gain of weight amount- 

 ing to only 480 grams at the end of the experiments, increased 



