84 MATHILDE L. KOCH AND OSCAR RIDDLE 



been analyzed apart from the rest of the brain (cerebellum and 

 medulla). These ten samples were selected with the purpose of 

 supplementing our previous results in the following respects: 

 a) To obtain information concerning the localization (cerebrum 

 or cerebellum-medulla) or non-localization of the previously ob- 

 served chemical changes in the brain of the affected birds; b) a 

 further comparison of the chemical constituents of the ataxic 

 and the normal brain; c) the persistence or non-persistence of 

 such differences in older birds; d) the extension of our knowledge 

 of the relation of age 2 to the chemical composition of the brain. 



MATERIALS ANDJMETHODS 



The brains used in the preparation of samples I, II, III, IV, 

 and VI are from birds similar to those used in our previous study 

 except for age differences. The two groups of ataxic birds showed 

 the disorder to different degrees. The older group (sample III) 

 being clearly the more affected. 3 The birds which supplied the 

 material for sample VI were considerably younger than the 

 birds used in the earlier study, while the other four samples were 

 obtained from somewhat older birds (II and IV), and from much 

 older (I and III) birds. The birds used in the preparation of 

 sample VI were mostly too young to classify as normal or ataxic. 



All of the above-mentioned birds, like those used for the pre- 

 vious study, were birds descended from the first obtained ataxic 

 or affected individual. These birds, ataxics and normals, were 

 therefore considerably inbred. The normals or 'controls' of 

 these groups were of the same strain and parentage as the ataxics; 

 they were, in the main, brothers and sisters of the ataxics. Sam- 

 ple V contained the brains of the oldest common pigeons (mostly 

 homers) of the same general kind, but without ataxic blood, which 

 we could obtain from our collection. 



In the present study the cerebrum was analyzed separately 

 from the cerebellum-medulla in four cases; i.e., four groups of 



2 Precise information of this sort has been obtained hitherto, so far as we are 

 aware, only in man and in the rat. The data for man are very incomplete. 



' The reader should consult our earlier papers for adequate descriptions of the 

 various manifestations or degrees of manifestation of the ataxia. 



