COMPOSITION OF BRAIN OF ATAXIC PIGEONS 105 



offspring (to the fourth generation) of the original ataxic female. 

 These data indicate that the ataxia does occur more frequently 

 among females if the computation be made upon offspring which 

 live long enough to permit a reasonably accurate prognosis of 

 ataxia or normality. Obviously, no other method of computa- 

 tion is practicable. 



Necessary to a full consideration of these particular figures are 

 the facts, published earlier by one of us (Riddle, '18), that the 

 ataxia does not behave as a sex-limited character in heredity, 

 and that probably more affected than unaffected individuals die 

 early — before definite classification as ataxic or normal is pos- 

 sible. Also, fully as many females as males die early. Included 

 in the group of birds that were properly classified for the above 

 purpose are a total of seventy-seven males and seventy-five 

 females. Among these there were, however, only fifteen ataxic 

 males to twenty-nine ataxic females. It is therefore quite prob- 

 able that females are more subject to the derangement than are 

 males. 



Comparisoii of constituents of parts of human and pigeon brain 



As a result of our separate analysis of anterior and posterior 

 parts of the brain, it is now possible to make a comparison of these 

 with similar parts of the human brain. So far as we are aware, 

 there are no data for other animals which permit a similar com- 

 parison with the parts of the human brain. The comparison is 

 best made by reference to table 9. A study of the figures ob- 

 tained brings to light the rather surprising situation stated below. 



The human cerebrum has, of course, higher values for certain 

 chemical components and lower values for certain other compo- 

 nents than the human cerebellum-medulla. The same is true for 

 the corresponding parts of the pigeon's brain. The singular 

 fact to which attention is directed lies in the circumstance that 

 in the pigeon the direction of the difference is the reverse of that 

 for man in the case of every chemical fraction shown in the table. 



Perhaps this incongruity will not be made less intelligible by 

 the immediate statement of another peculiarity of the figures of 



