Fred C. Koch 107 



fed for three or f >ur days with cracker dust made into pellets of known 

 weight. At the close of this preliminary feeding the unconsumed material 

 was weighed and from this the average amount eaten per day determined. 

 For ten days following this period each mouse then received this weight 

 of cracker dust, with the incorporated iodine-containing substance, in 

 the form of pellets. The control mice were fed in the same way with 

 plain cracker dust pellets. At the end of the 10-day feeding period the 

 acetonitrile was injected subcutaneously. Each dose administered in 

 series I, II and III was contained in 1 cc. of fluid; in series IV-IX, in 0.5 

 cc.; in series X, in 0.66 cc. In most cases the animals consumed the food 

 very well. All the mice used were raised in the laboratory building on a 

 diet of milk and crackers with occasional bits of lettuce until used for the 

 experiment. Care was taken to compare mice of as nearly the same age as 

 possible. In the tables below the litter number of each mouse is given. 

 The ages of the mice of the various litters were as follows : Litter 2, 119 days; 

 litter 3, 102 days; Utter 4, 100 days; litter 5, 80 days; litters 6 and 10, 99 and 

 113 days respectively; litter 9, 115 days; litters 11-12, 125 and 135 days 

 respectively; litters 13-14, 144 and 151 days respectively; litter 28, 85 days; 

 litters 29-30, 59 and 66 days respectively; litters 31, 32 and 34, 95, 85 and 97 

 days respectively; litters 33-35, 101 and 89 days respectively; litters 36-37, 

 89 days; litter 38, 79 days; litters 56-60, 91-103 days. 



C. Discussion of the physiological tests. 



Thyreoglobulin. Series I shows that thyreoglobulin possesses 

 the full activity per unit of iodine when compared with the dried 

 thyroid from which it was prepared. This is also confirmed by 

 series IV where a decomposition product obtained from the 

 globulin still shows the complete activity per unit of iodine. 

 The whole of the physiological activity of the gland is therefore 

 quantitatively in the thyreoglobulin. 



Metaprotein. As stated above, this still shows the full activity 

 per unit of iodine although the percentage concentration of iodine 

 has increased from 0.465 per cent in the thyreoglobulin to 1.52 per 

 cent in the metaprotein. 



lodothyrin. None of the iodothyrin preparations tested was 

 found to bring about a resistance to acetonitrile more than three- 

 fourths of that produced by the thyroid-tissue fed mice. The indi- 

 cations are that these preparations are all about equally inactive, 

 lodothyrin is therefore less active per unit of iodine than the thyreo- 

 globulin. See series III and V. 



Primary albumose. This is still very active, as shown by series 

 IV and VII; although the full activity per unit of iodine is not 



