COMPOSITION OF BRAIN OF ATAXIC PIGEONS 85 



brains yielded materials for eight analyses. The two additional 

 analyses, samples V and VI, were of entire brains, although here 

 also the cerebrum was weighed separately from the rest of the 

 brain. 



The birds were all killed by decapitation and the brain removed 

 immediately, using the following technique: After removing the 

 feathers and skin, the skull was opened at the posterior end. 

 The dorsal surface of the medulla and cerebellum was exposed 

 up to the point of the anterior border of the cerebellum by re- 

 moval of the skull and meninges. The cerebellum was then 

 turned back until the posterior border of the optic lobes was 

 exposed. The separation of cerebellum and anterior region of 

 the brain was affected by cutting just posterior to the cerebral 

 peduncles and the posterior border of the optic lobes. The me- 

 dulla and cord were severed at the foramen magnum and the 

 posterior brain weighed (between watch-glasses) immediately. 



The remainder of the dorsal and anterior skull was next re- 

 moved. The olfactory nerves were cut and the cerebrum turned 

 back so as to expose the optic chiasma. The optic nerves were 

 severed about 1 mm. anterior to the chiasma. The cerebrum 

 was removed by tilting it backward and cutting the cranial nerves 

 close to the brain. It was then immediately weighed (between 

 watch-glasses) and placed in a sufficient quantity of redistilled 

 alcohol to make the final concentration of alcohol about 85 per 

 cent. Analysis was begun two months after the collection of the 

 material. 



The method used in the analysis of this material is that of 

 Waldemar Koch ('09) and the same 4 as was used in the previous 

 study. 



PRESENTATION OF DATA 



Our earlier work with the brain of the pigeon made it evident 

 that it is necessary to obtain data on the age, sex, body weight, 

 and normality or abnormality of each bird whose brain was col- 

 lected for chemical analysis. These data for the birds used in 



4 The method has been recently republished with slight modification by M. 

 L. Koch and C. Voegtlin ('16). 



