92 MATHILDE L. KOCH AND OSCAR RIDDLE 



direction of the normal female. It will be pointed out later that 

 ataxia is found more often in females than in males. Since the 

 observed effects of ataxia on the male all take the direction of 

 the female, it may be asked, does this fact have any bearing upon 

 the predominant appearance of the derangement in female 

 offspring? 



Before concluding the above considerations (in which the mate- 

 rials entering into the composition of the samples are being con- 

 sidered as fully as a paper presenting chemical data permits), 

 emphasis may be placed upon the fact that samples I-Ia and 

 III-IIIa (older normals and older ataxics), though quite com- 

 parable as to age, are not so in regard to sex. Also, that this sex 

 difference at least partially accounts for the size differences of 

 the brains of these two groups. And, further, that differences of 

 brain size may be of significance in the results of the chemical 

 analysis. Donaldson ('16) obtained from the rat evidence "that 

 both the relative and absolute weight of the brain * * * , at a 

 given age, are factors tending to modify the percentage of water 

 present, in the sense that the heavier brain or cord shows the 

 smaller percentage of water." Donaldson 7 also indicates that in 

 a given species the larger (heavier) brains at a given age tend to 

 have a higher percentage of white substance. On this basis the 

 larger brains of both the older and younger normals (samples 

 I-Ia, II-IIa) might be expected to show lower water values 

 (and other chemical evidences of greater age) than the ataxic 

 groups of somewhat smaller brain size with which they are com- 

 pared. Possibly such size relations do slightly influence the 

 amount of the various chemical fractions obtained by us. We 

 would note, however, that the cerebrum of the younger normals 

 (Ila) and the younger ataxics (IVa) were of equivalent (total) 

 size (14.252 grams and 14.233 grams, tables 1 and 2), and in 

 each sample the sexes were equally represented; nevertheless, 

 when the figures obtained for these two groups are compared, 

 on the basis of the nine constituents found to be characteristic 

 of age in this series (p. 98), it is found that six of these nine con- 

 stituents here indicate the relative immaturity of the ataxic 



7 Personal communication. 



