234 SWALE VINCENT 



bodies and kidneys. The results confirm the generally accepted doctrine 

 that hyperthyroidism produces a general acceleration of metabolism. 

 Hoskins could not find any constant changes in the thyroid gland. 



Herring (&') carried out a series of experiments in which each thyroid- 

 fed animal and its control were taken from the same litter. He adminis- 

 tered fresh ox-thyroid in daily amounts of from 0.1 to 0.2 gram. (This 

 would correspond to 25 to 50 mg. of dried thyroid daily.) The control 

 male rats (3) gained an average of 69 grams' in 25 days. The thyroid-fed 

 males gained 65 grams. In the female rats the controls gained on an 

 average 2 grams more than the thyroid fed. 6 There was considerable 

 variation among the female animals, which were more susceptible to the 

 treatment than the males. 



Cameron and Carmichael have recently tested the effect of thyroid 

 feeding on white rats. They have taken the precaution to use animals 

 from the same litter for comparison. Males and females were compared 

 separately. Their dose was always based on the body weight of the animal 

 at the time of treatment and was relatively small compared with that 

 employed by previous observers. Some of the control animals were fed 

 with liver substance instead of thyroid, and this was found not -to affect 

 the curve. They think that toxic effects may be ruled out. 



The body-weight was found uniformly smaller in the thyroid-fed 

 animals. The difference in weight between the control and the thyroid 

 rats after prolonged feeding tends to diminish or disappear. This is at 

 any rate true in females. The results appear to show that size of the 

 dose has very little effect. This conclusion is opposed to that of previous 

 observers. The thyroids of all the treated rats were paler than those of 

 the controls. 



The chief facts established by these experiments ar3 that thyroid 

 feeding inhibits the growth of young white rats, at any rate for the period 

 of eight or nine weeks, and that iodid has no effect. These experiments 

 afford the first definite chemically controlled test for thyroid as against 

 iodid. 



Kojima finds that thyroid administration as well as the giving of Nal 

 and KI to the rat causes accumulation of colloid in the thyroid (v. Fordyce 

 supra) and the epithelium of the vesicles become flattened. The cells of 

 the parathyroid are generally swollen. This observer records diminution 

 of body weight as a result of thyroid feeding. There is also hypertrophy 

 of the pancreas accompanied by the occurrence of numerous mitotic 

 figures in the nuclei and alterations in the granules of the cells. 



We must now treat briefly a subject well known to students of endo- 

 crinology under the name of "experimental hyperthyroidism." 



6 Jn consideration of the variability of growth in rats of the same litter this 

 difference cannot be regarded as significant. R. G. H. 



