200 G; E. COGHILL 



lost the characteristic crossed reflex, be immersed in a solution of 

 curare, the extent of the movement in response to tactile stimu- 

 lation gradually becomes reduced, and the forms of movement 

 go out of the behavior in the reverse order to that according to 

 which they appeared, that is to say, the effective swimming move- 

 ment gives place to feeble S-reactions ; these, to coiled-reactions ; 

 these, to feeble flexures; till eventually only the slightest head 

 movement occm^s, and finally responses of all kinds cease. Now, 

 during the later period of the decline in motility, when be- 

 havior has reverted to the earlier type, the regularity of crossed 

 response reappears, and through long series of responses the 

 movements will be constantly away from the side stimulated. 

 The most obvious inference to be drawn from this recurrence in 

 the form of behavior is that the progressive paralysis of the motor 

 nerve endings by curare eliminates more and more the stimu- 

 lations of the muscle sensory endings of the giant ganglion cells, 

 and the associative center or motor column, one or both, are left 

 to the almost exclusive stimulation from localized cutaneous areas. 



These results from experiments with curare are confirmed 

 by another simple form of experiment, namely, the transection 

 of swimming embryos at about the level of the pectoral limb bud, 

 so as to leave in the head piece just enough muscle to give a per- 

 ceptible contraction when observed under the microscope. The 

 head piece of such a transected embryo, it is found, through long 

 series of reactions approaching a hundred in rapid succession, 

 contracts the muscles constantly on the side opposite the stimulus. 

 Here, again, the associative and motor centers have been severed 

 from the influence of the greater part of the trunk, and the domi- 

 nating factor of the trunk as compared with the cranial field of 

 stimulation is the muscle system. 



From such experiments as these, it seems necessary to conclude 

 that the giant ganglion cells have a proprioceptive field of stimu- 

 lation through their endings on the myotomes, and that this field 

 of stimulation has a profound influence over the behavior of the 

 animal when it responds to localized cutaneous stimulation. This 

 primitive reflex mechanism, therefore, exhibits the phenomena of 



