86 COM PAR A TIVE PHYS1OLOG Y OF THE BRAIN 



muscles of the aboral piece to contract reflexly or 

 perhaps directly. In this way, therefore, coordina- 

 tion between the oral and aboral piece is possible in 

 spite of the interruption of the nervous connection. 

 Friedlander obtained further proof of this by divid- 

 ing worms completely and connecting the two halves 

 by strings. Even then he found that the aboral piece 

 moved with the anterior piece in a perfectly coordin- 

 ated way. These facts prove that the brain has no 

 leading role in the coordination of the progressive 

 motions of the earthworm. 



What part, then, does the central nervous system 

 play in the coordination ? It serves only as a quick 

 conductor for the stimuli. Friedlander has shown 

 that the quick motions which an earthworm shows 

 upon a sudden stimulus are no longer transmitted 

 to the posterior part of the body if the ganglion- 

 chain be severed. If the nervous connection be 

 broken so that stimuli cannot be conducted through 

 the nerves, the peripheral structures suffice to make 

 coordinated movement possible. 



One might suppose the coordination in the pro- 

 gressive movements of higher animals to be of an 

 entirely different nature from that of worms. An ob- 

 servation made by Goltz, however, shows that in 

 dogs, at least, this is not the case. When a dog with 

 divided spinal cord is lifted up by its fore-legs, so that 

 the back part of the body hangs down perpendicu- 

 larly, a remarkable phenomenon may be observed. 

 The hind-legs perform pendulum motions which 



