310 E. R. HOSKINS 



to age. On the whole, the correspondence with the Wistar 

 tables is as close as could be expected. The individual organs 

 will be considered later. 



b. Effects of thyroid, thymus, hypophysis and pineal feeding. 

 The weight and length of the growing albino rats fed various 

 ductless glands are shown in tables 6 and 7, and (for the 'higher 

 dosage' groups) in charts 3 and 4. For the sake of elimination 

 of any variation that might be due to the age of the rats, each 

 sex group was subdivided into 2 smaller ('old' and 'young') 

 groups, depending upon the age of the individuals. Some of 

 the younger animals received fresh and some dried glands (see 

 'Material and Methods'), but no difference was noticed in the 

 effects produced by the two forms. 



The effect of a ductless gland diet upon the growth of the 

 females is seen in table 6 and chart 3. The various experimental 

 groups may be compared with each other or with the controls, 

 and it is found that the difference in weight at every age is 

 remarkably slight. At the beginning of the experiment when 

 the rats were 3 weeks old the different groups averaged nearly 

 the same in weight, excepting the male thyroid group and the 

 pineal groups. Into these groups were purposely placed slightly 

 more than their share of smaller animals because it has recently 

 been claimed that thyroid and pineal substances accelerate 

 growth in various species (Schiifer '12) (Dana and Berkeley 

 '13, McCord '14). At 70 days of age, when the period of most 

 rapid growth had ended, it is seen that among the younger ('high- 

 er dosage') animals there had been a remarkably small difference 

 in the growth rate of the various groups. The same is true of the 

 older rats, if the thyroid group (which contains 2 rats that were 

 not healthy) is left out of consideration. At 90 days of age the 

 weights of the different groups still remain fairly close together. 

 After 70 days the groups are no longer directly comparable because 

 many of the rats had been killed. Upon the comparison of 

 individuals within each litter, no constant difference appears, 

 although considerable variation is shown. The only probable 

 conclusion to be drawn is that the glandular substances (in 



