NERVOUS CONTROL OF ANIMAL MOVEMENTS. 353 







side experiences a permanent contraction. This attitude is so regular in 

 these lesions that, from simple sight, we can indicate the direction of the 

 movement of rotation. The opposite side has also a constant and 

 typical attitude ; the throwing out of the fore-leg from the thorax is 

 always as is shown Fig. 4. 



When this frog is placed in water it turns on itself, the right side 

 serving as the axis of movement. When it is at rest in the water, it 

 takes the attitude represented in the figure. The right half of the body 

 sinks in the water; the-limbs of this side can never be on a level with 

 those of the opposite side. These last, on the contrary, especially 

 when the cerebral lobes are removed from the two sides, float on the 

 surface and counterbalance the influence of the opposite side ; the hind- 

 foot of the uninjured side remains extended, and rests always at a 

 higher level than that of the opposite side ; the fore-foot comes out of 

 the water, as well as the anterior part of the body. The limbs of the 

 affected side are not really paralyzed, but, nevertheless, their move- 

 ments are more limited, they are not so extended nor so various, and 

 their action no longer coincides with that of the healthy side. 



Fig. 5. 



A Frog, in which the Pons Varolii has been mutilated on both Sides. 



If, in place of pricking or deeply wounding one side of the pons 

 Varolii, we prick or wound these nervous centres on each side, a little 

 above the bulb, we obtain a tonic contraction of both sides of the body, 

 and the frog takes the attitude represented in Fig. 5, an attitude due, 

 without doubt, to a tonic contraction of all the muscles of the body. 

 Put in the water, this frog falls to the bottom and remains motion- 

 less. 



Considering successively the attitudes taken by the frogs from Fig. 

 2 to Fig. 5, we see perfectly that, when we get beyond the cerebral 

 lobes, all lesion of the other parts of the encephalon leads to a sort of 

 23 



