ix MID- AND INTEE-BKAIN 503 



placed on the edge of a table they often went over it and fell to 

 the ground. They stumbled against obstacles ; the brightest 

 light and blackest dark produced no effect other than a pupil 

 reaction (myosis or mydriasis). If flung into the air they always 

 fluttered down, and on reaching the ground continued to flap 

 their wings for some time before they became quiet; they 

 blundered against obstacles during their flight, and if this was 

 impeded, tumbled to the ground. 



In seeking to account for the disparity between these results 

 of Munk and those previously described with no less care by 

 Longet, we were led to - think (1885) that the four pigeons 

 examined by Murik had become blind from the effects of degenera- 

 tion descending to the thalami and optic lobes, which Munk did 

 not examine directly. It is certain that the more recent experi- 



Fio. 257. A, brain of normal pigeon from nature, enlarged J. a-c, brain of a pigeon in which 

 Schrader had extirpated both hemispheres, sparing the optic thalami and optic lobes also 

 magnified J. a, from behind ; b, from front ; c, from the side. 



ments of Schrader (1889), due to the effects of total destruction 

 of the cerebral hemispheres of pigeons, accurately performed, pro- 

 duced a perfectly different set of symptoms from that described 

 by Munk. 



Schrader lost 75 per cent of the animals operated on, fourteen 

 pigeons survived. Many of these were killed after four months, 

 after they had been closely and frequently examined. Some died 

 in the fourth or fifth week with signs of progressive weakness, 

 probably the effect of descending degeneration. The post-mortem 

 examination performed by Kecklinghausen showed completely 

 successful ablation of the hemispheres with no lesion of the optic 

 thalami. 



In the first three to four days after the operation, according 

 to Schrader, there is the condition of sleep and absolute immobility 

 described by Rolando and Flourens. After this period the animals 

 begin to move about in the laboratory, very slowly at first and 

 quicker by degrees till they recover their normal gait. This 

 active movement cannot be ascribed to traumatic irritation, since 



