CENTRAL NERVOUS SYSTEM. 267 



and the optic nerves being left intact. For the Hist few days after the 

 operation the bird is in a sleep-like condition. Next the sleep becomes 

 broken into shorter and shorter periods, and then the bird begins walking 

 about the room. From the beginning- its movements are directed by vision ; 

 slight obstacles it surmounts by flying up to them, larger ones it goes around. 

 In climbing, its movements are co-ordinated by the sense of touch, and the 

 normal position of the body is maintained with vigor. The birds which walk 

 about by day remain quiet and asleep during the night. In flying from a 

 high place the operated pigeon selects the point where it will alight, and pre- 

 fers a perch or similar object to the floor. 



A reaction to sound is expressed by a start at a sudden noise, like the 

 explosion of a percussion-cap. 



Pigeons without the cerebrum do not eat voluntarily, though the presence 

 of the frontal portions of the hemispheres is sufficient to preserve the reac- 

 tion. 



In a young hawk slight damage to the frontal lobes abolished for the time 

 the use of the feet in the handling of food, and thus abolished in this way the 

 power of feeding as well as that of standing. 



With the loss of the cerebrum the pigeon does not lose responsiveness to 

 the objects of the outer world, but they all have an equal value. The bird is 

 neither attracted nor repelled, save in so far as the selection of the points 

 toward which it will fly is an example of attraction. Sexual and maternal 

 reactions both disappear, and neither fear nor desire is evident. 



In ascending the mammalian series, the removal of the cerebrum becomes 

 a matter of increasing difficulty. The reasons for this are several, and reside 

 in the increasing size of the blood-vessels and the nutritive complications 

 dependent on the increase in the mass of the cerebrum, as well as in the 

 greater physiological importance of this division. Goltz 1 has been able by 

 repeated operations to remove the entire cerebrum of a dog, and still to keep 

 the animal alive and under observation for eighteen months, at the end of 

 which time the animal, though in good health, was killed for further exami- 

 nation. This dog was blind, though he blinked when a very bright light 

 was suddenly flashed in his face. He could be awakened by a loud sound, 

 and when awake responded to such sounds, when intense, by shaking the head 

 or ears. This would not, however, be complete proof that lie could hear. 

 The sense of taste was so far present that meat soaked in quinine was rejected 

 after tasting. Tactile stimuli and those involving the muscle sense. as in the 

 case where the animal was lifted, caused him to struggle and to bid' in the 

 direction of the irritation. These reactions were modified according to the 

 locality of the stimulus. The power to make movements expressive of pain 

 was still present. 



On the motor side the dog was capable of such highly complicated acts 

 as walking, standing, and eating, and in these operations was guided by the 

 muscle-sense and that of contact. The sexual instincts were lost, but the 

 1 Archiv fur die gesammte Physiologie, Bd. xli. 



