EXPERIMENTAL STUDIES ON THE THALAMUS 23 



November 11. Reflexes sluggish (to irritants); no spontaneous move- 

 ments; pupils dilated. 



November 13. Temperature subnormal; stands unsteadily on its 

 feet; pupils dilated. 



November 16. Bird seems weak; swallows water readily; unable to 

 stand steadily; uses its tail to support itself; pupils constricted and no 

 eye nystagmus on rotation of bird. 



November 18. Bird died. 



Examples of this sort could be multiplied indefinitely. Decer- 

 ebration with combined thalamic lesions of one kind or another 

 have been done on sixty birds. The details have varied consider- 

 ably from bird to bird. In an attempt to analyze this variable 

 complex, two factors stood out as at least essential. First, in 

 each different experimental animal it is probable that there were 

 some detailed differences in the amount of brain-stem tissue 

 injured; and, secondly, attention was gradually drawn to the pos- 

 sible influence of the body temperature variations. This latter 

 problem was then approached and a specific study made of body 

 temperature regulation after thalamic injury. This has been 

 reported elsewhere in detail. 



With reference to the first factor, it seemed evident that it 

 could only be controlled by a careful series of histologic prepara- 

 tions of the remaining brain tissue after a detailed study had 

 been made of the behavior of the animal during life. In accord- 

 ance with these principles, a bird was prepared by the usual 

 method of decerebration with what was thought to be a thor- 

 oughly complete destruction of the thalamus. A careful record 

 of the behavior of this animal was kept with due regard to the 

 control of the body temperature, and after death serial sections 

 were cut of the parts of the brain that were still intact. The 

 writer can therefore state definitely the changes in behavior and 

 reflex activity of this bird with wide changes in body tempera- 

 ture with a definite statement of how much of the brain was his- 

 tologically intact at time of death. 



