304 E. R. HOSKINS 



data the difference in the two conditions of the material adminis- 

 tered was disregarded. 



The rats used, were grouped to exclude so far as possible the 

 error introduced by the racial variability. One rat of each litter 

 (or one of each sex if both males and females of the litter were 

 used) was kept for control, the remaining being distributed 

 among the groups treated, in such manner that (so far as possible) 

 each group contained individuals from every litter. There 

 are five groups of each sex. To eliminate the 'age' factor, the 

 data for each sex were subdivided into 'older' and 'younger' 

 groups, as shown in the tables. 



In calculating the results, two methods were used. In one 

 the average of the percentage of the net body weight of each 

 organ of each group of experimental animals was compared 

 directly with the average value of that organ in the control 

 group while in the second method a comparison was made with 

 the Wistar reference tables as suggested by Donaldson ('15). 

 In the latter comparison the gross body weight was used instead 

 of the length because the weight of the organs of the controls 

 corresponded somewhat more closely to Donaldson's Wistar 

 norm for rats of the same gross body weight than to those of 

 the same length. The values obtained, however, would have 

 been practically the same in either case. 



The tables published by Donaldson ('15) used here are desig- 

 nated as 'Donaldson's Wistar tables' or the 'Wistar norms.'' 



For the dosage employed see table 3. 



The experiments began when the rats were weaned, at the 

 age of about 3 weeks, excepting 15 rats which were 8 to 11 weeks 

 old. Of these 15 rats, only 4 were autopsied. Each rat was 

 treated on alternate days throughout the entire period of the 

 experiment. Nine litters were given fresh glandular substance, 

 and all others received dried glands. The material to be fed 

 was mixed with a small amount of bread and milk and the ani- 

 mal kept in an individual cage until all of this had been eaten. 



