REMOVAL OF THE CEREBRUM FROM A FROG. 



68 3 



sleep, it takes no food, it has no feelings of hunger and thirst, it shows no symptoms 

 of fear, and ultimately, if left alone, it becomes desiccated like a mummy on the 

 spot where it sits. [If the flanks of such a frog be stroked, it croaks with the 

 utmost regularity according to the number of times it is stroked. Langendorff has 

 shown that a frog croaks under the same circumstances, when both optic nerves 

 are divided. It seems to be influenced by light; for, if an object be placed in 

 front of it so as to throw a strong shadow, then on stimulating the frog it will 

 spring not against the object, a, but in the direction, 6 (fig. 471). Steiner finds 

 that if a glass plate be substituted 

 for an opaque object like a book, 

 the frog always jumps against this 

 obstacle. Its balancing move- 

 ments on a board are quite re- 

 markable and acrobatic in charac- 

 ter. If it be placed on a board, 

 and the board gently inclined (fig. F i g> 471> 

 472), it does not fall off, as a frog Fig . 47l.-Frog without its cerebrum avoiding an ob- 

 with only its spinal cord will do, ject placed in its path. Fig. 472. Frog without its 

 but as the board is inclined, so as cerebrum moving on an inclined board (Goltz). 

 to alter the animal's centre of gravity, it slowly crawls up the board until its equi- 

 librium is restored. If the board be sloped as in fig. 472, it will crawl up until it 

 sits on the edge, and if the board be still further tilted, the frog will move as indi- 

 cated in the figure. 1\ only does so, however, when the board is inclined, and it 

 rests as soon as its centre of gravity is restored. It responds to every stimulus 

 just like a complex machine, answering each stimulus with an appropriate action.] 



A pigeon without its cerebral hemispheres behaves in a similar manner (fig. 

 473). When undisturbed it sits continuously, as if in sleep, but when stimulated, 

 it shows complete harmony of all its 

 movements ; it can walk, fly, perch, and 

 balance its body. The sensory nerves 

 and those of special sensation conduct 

 impulses to the brain ; they only dis- 

 charge reflex movements, but they do 

 not excite conscious impressions. Hence, 

 the bird starts when a pistol is fired close 

 to its ear ; it closes its eyes when it is 

 brought near a flame, and the pupils con- 

 tract ; it turns away its head when the 

 vapour of ammonia is applied to its nos- 

 trils. All these impressions are not per- 

 ceived as conscious perceptions. The Pigeon with its cerebral hemispheres removed, 

 perceptive faculties the will and memory are abolished ; the animal never takes 

 food or drinks spontaneously. But if food be placed at the back part of its throat 

 it is swallowed [reflex act], and in this way the animal may be maintained alive 

 for months (Flourens). 



Fish appear to behave differently. A carp with its cerebrum removed (fig. 483, 

 VI. 1) can see and may even select its food, and seems to execute its movements 

 voluntarily (Steiner, Vulpian). 



Mammals (rabbit), owing to the great loss of blood consequent on removal of the 

 cerebrum, are not well suited for experiments of this kind. Immediately after the 

 operation they show great signs of muscular weakness. When they recover, they 

 present the same general phenomena ; only when they are stimulated they run, 

 as it were, blindfold against an obstacle. Vulpian observed a peculiar shriek or 

 cry which such a rabbit makes under the circumstances. Sometimes even in man 



