102 



MATHILDE L. KOCH AND OSCAR RIDDLE 



readily compared (figures for both placed in italics) with the 

 brains of similar ages. It is in these two series in which the ab- 

 normality was most marked that the clearest evidence for a 

 chemical under-differentiation or relative immaturity of the 

 ataxic brains is found. It is notable that in both of these groups 

 the amount of water is either equivalent to or more than is indi- 

 cated for their actual age; protein is present in excess in both; 

 lipoids are deficient in both; cholesterol is lowest in both; phos- 

 phatids and sulphatids 14 are also low in both; total phosphorus 



TABLE 8 



Chemical composition of the ivhole brain of normal and ataxic pigeons (in per cent 



of solids) . Arranged according to age 



1 Birds not of ataxic strain, but of nearly similar variety. 



2 A mixed group, probably normals and atax'cs, all from ataxic strain. 

 Note. — Nos. 1 to 5 and 11 are new data; nos. 6 to 10 are our earlier data ('18). 



is low in both; extractive-phosphorus and protein-phosphorus 

 are high in at least one case. In all of these fractions these two 

 ataxic brain groups are less differentiated chemically than brains 

 of their calendar age should be. Extractives are not distinctive 

 of age for the ages actually considered and one ataxic shows a 

 high the other a low figure for this fraction. 



It thus appears that of those nine chemical fractions (eighteen 

 for the two groups) which can be relied upon to reflect age differ- 



14 Confirmed by lipoid-phosphorus and lipoid-sulphur, table 7. 



