35 2 THE POPULAR SCIENCE MONTHLY. 



were lacking, nor could it even plunge, which wild-ducks usually do 

 when wounded, if they cannot fly. Notwithstanding the approach of 

 the dog, and the evident very energetic action which its brain sought 

 to exert at this moment on its movements, it could only swim on the 

 surface of the water with a forced movement of rotation. 



When the lesion is made on the two sides, some of the same phe- 

 nomena are seen ; only, as the stimulus to activity on both sides is the 

 same, the animal moves in a right line. We have injected mercury in 

 an opening made with a trepan into the upper part of the cranium of 

 a young cat. In a little while, the mercury, by its weight, having 

 reached the base of the brain, the animal lifted himself up, and plunged 

 forward against the wall, making vain efforts to go straight on ; deviat- 

 ing to one side, he continued his course till he encountered a new ob- 

 stacle, and so on. He stopped only when exhausted, and yet until his 

 death from compression of the bulb, his limbs moved without inter- 

 ruption. 



In a man who had all the symptoms of a cranial tumor, we have 

 observed phenomena almost identical with these presented by this 

 young cat. When he had a crisis, he would raise his haggard eyes, 

 and walk straight in his chamber, being guided only by the reflex ac- 

 tion of locomotion and by habit. After his crises, he could not remem- 

 ber having walked. 



It is evident that, in these cases, it cannot be a question of paralysis, 

 and that the phenomena are the result of excitation of the locomotive 

 centres. If the influence of the cerebrum, on one side, is obliterated, 

 and the locomotive centres are not irritated, they act only when they 

 are solicited to activity by. movements impressed by the opposite side, 

 and then these movements are forced and automatic, but regular and 

 without exaggeration. The result is, a movement in a circle, which 

 occurs when the animal can change his place. If, on the contrary, the 

 centres are directly excited, the impulse is forced, and the animal is 

 obliged to move in the way impressed by the centres. 



Better to comprehend the rolling movements, we must explain 

 some facts which have not been dwelt upon, and which we observe in 

 animals in repose. In lesions of the cranial centres, when we wound 

 the pons Varolii, the animal has no longer the same exterior carriage ; 

 he leans to one side or the other, according to the side where the lesion 

 is made. All the muscles of this side are then in a state of permanent 

 contraction. The frog represented in Fig. 2, from which have been re- 

 moved only the cerebral lobes of the two sides, is remarkable for the 

 regularity and the symmetry of the position of his limbs. Placed in 

 the water, he rests on its surface, and the right side is at the same level 

 as the left side. But, if we wound the cerebellum on one side, whether 

 the cerebral lobes are intact or removed, at once the exterior carriage 

 becomes that which is represented in Fig. 4. In this frog, the cerebel- 

 lum has been destroyed on the left side, and instantly the entire right 



