350 THE POPULAR SCIENCE MONTHLY. 



was chloroformed ; the left side, which was more drawn up, where the 

 muscles experienced a tonic contraction predominating over those of 

 the right side, became then more feeble. This effect became more 

 and more pronounced in proportion as the chloroform took effect, up 

 to the time when the two sides were completely affected ; then the frog 

 would no longer rest on his fore-feet, and the hind-feet remained ex- 

 tended and motionless. In proportion as the anaesthesia disappeared, 

 the feet of the healthy side folded themselves and approached the 

 body ; those of the opposite side remained still extended. Then these 

 folded themselves similarly. The attitude of the two sides was then 

 identical, but, when the normal state was recovered, the limbs on the 

 side affected by the cerebral lesion again became more drawn up, and 

 the body leaned on that side. 



In this frog we have again on one side the influence of the cerebral 

 lobes, but, on the other side, the locomotive centres are completely in- 

 dependent, and they act alone on the movements which take place on 

 the corresponding side of the body. What happens, then, when the 

 animal attempts to move ? From the healthy side the movements are 

 made according to the desire and the will, they are limited to the end 

 wished by the animal ; but, on the other side, they are made en masse, 

 automatically, invariably ; they drag the animal from their side ; at 

 the same time, the mathematical regularity of their contractions be- 

 comes, so to say, a dynamic centre for the movements of the opposite 

 side, which are less regular. In this way we explain the movement in 

 a circle, the side in relation with the wounded part being in the interior 

 of the circle made by the animal. This also is the reason why such 

 movements, particularly when the circumference is small, occur only 

 when the animal can change his place, and very often commence only 

 after the first moments of locomotion. 



In case the cerebral influence is abolished, the locomotive centres 

 become absolutely independent, as is shown by the forced automatic 

 movements. Again these centres may be excited by a tumor, or a 

 prick, and then their dependence upon the cerebral lobes ceases at 

 once, notwithstanding the anatomical communications which still exist. 

 It is in these cases that the compulsion, from the instant of the lesion, 

 becomes invincible, and forces the animal into movement. The loco- 

 motive centres become active, and, as long as the excitement lasts, the 

 animal is completely under their influence. Neither the will, nor emo- 

 tion, nor physical obstacles, can prevent the limbs from moving. 



A hunter gave us the following account : From a considerable dis- 

 tance he had shot at some wild-ducks that were on the water ; one of 

 these ducks was not able to fly, and remained on the water, turning in 

 a circle. This duck had received a superficial wound from a grain of 

 lead in the side of its head ; it had absolutely no other wound on its 

 body. Now, the curious fact, and what astonished the hunter, was, 

 that this duck could not fly, and yet neither the will nor the means 



