622 



PHYSIOLOGY OF THE BRAIN-STEM 



ments : in walking the limbs are lifted too high, extended too far and sometimes 

 are set down too far to one side or the other; the result is that the carapace 

 wabbles from side to side and strikes the floor first with one corner, then with 

 the other. 



The chief difference between the lizard and the turtle and the lower verte- 

 brates after removal of the cerebrum, it would seem., is that they do not 

 spontaneously take food,, while the lizard also does not move at all spontane- 



Ifactory lobe 



Forebrain 

 (hemispheres) 



Midbrain 



(optic lobes) 

 Hindbrain 



(cerebellum) 



FIG. 278. Brain of a pigeon, after Wiedersheim. The cranial nerves are numbered. 



ously. It is likely therefore that the cerebrum is not of the same importance 

 in animals of this grade as it is in the higher vertebrates such as birds and 

 mammals. But even in the latter it can be demonstrated that the lower parts 

 of the central nervous system can maintain a high degree of activity. 



Of the numerous observations on birds which have been made since the time 

 of Rolando, we shall cite only those of Schrader on pigeons. These animals in 

 Schrader's hands survived the operation of removing the cerebrum (Fig. 278) 

 for four to five weeks and died then as the result of progressive general weakness 

 which began about the fourth week. 



During the first three or four days they remained in a sleepy condition, 

 standing with feathers ruffled, head drawn in, eyes closed (and often on one leg), 

 just where they were placed. Now and then they would shake themselves, smooth 

 out their feathers with the beak, stretch themselves as if drowsy and, if desiring 

 to defecate, would take a few steps. When thrown up into the air, they made 

 flying movements but came obliquely downward, striking the wall or other obsta- 

 cles and rather falling to the floor than reaching it by "lighting"; then they 

 once more sank into a stupor. In short, the animals appeared bereft of all 

 initiative, and one would be inclined to declare them blind and deaf and to doubt 



