308 CARL RICHARD MOORE. 



animals and claiming for it partial proof for an hypothesis. It 

 appears that the claim of the writer is not only justified, but 

 proven, that the weight of an animal as a character indicating the 

 effect of a sex-gland graft is not only worthless as scientific data, 

 but very confusing to the entire problem of the modifying effects 

 of gonads. 



In reference to the effects of gonadectomy on the weight of the 

 glands of internal secretion, little will be added to the discussion 

 in connection with each section of the paper. The great dis- 

 crepancies in results, even diametrically opposed conclusions, of 

 different investigators working with the same groups of animals 

 have already been pointed out. The chief difficulties in adjusting 

 the results from the various sources appear to center around in- 

 adequate controls for the experiments. Should one desire to 

 study the effects of gonadectomy on such a structure as the hy- 

 pophysis, it should be obvious that animals of similar strains, 

 reared under similar conditions, operated at similar ages, and con- 

 trolled by the proper groups are essential. Variations in general 

 metabolism are not only so great among animals of different ages 

 and strains that isolated comparisons often indicate inconsistent 

 results, but even animals of the same litter may show marked 

 differences. 



The writer does not wish to imply that this experiment has been 

 conducted in an ideal manner, but an attempt has been made to 

 know, in so far as is possible, the history of the animal before and 

 after operation, and to afford comparisons of groups of consider- 

 able size rather than mere isolated comparisons. Furthermore, it 

 is realized that unknown conditions may have influenced the results 

 herein reported and repetition is highly desirable before they can 

 be accepted as of particular value. 



As to the influence of gonadectomy on bone growth, the above 

 criticisms apply as well. Growth in general body proportions is 

 to a certain extent relatively constant for various parts. It should 

 be supposed at once that a somewhat larger animal than a brother 

 or sister would be expected, in general, to have longer bones and 

 yet not show a specific reaction in bone growth conditioned by the 

 presence or absence of sex-gland secretions. 



The results of an analysis of the bone lengths of this group of 



