352 



STUDIES IN GENERAL PHYSIOLOGY 



touched a local contraction occurs at the stimulated point, 



but no progressive movements. 



4. If a lateral piece ab is cut from an animal parallel to 



the median plane (Fig. 101), a contraction of the wound results 



which may be so great tha % t the piece rolls up into a spiral. 

 (This contraction of the wound-edges 

 occurs no matter what the position of 

 the cut.) The lateral piece afr, which 

 contains no brain, executes no pro- 

 gressive movements. If, however, a 

 contraction of the wound-edge occurs 

 in the other piece, so that it is rolled 

 into a spiral, the progressive move- 

 ments no longer occur in a straight 

 line but in a circle. I never succeeded 

 in bringing about circular movements 

 through unilateral destruc- 

 tion of the brain in Thy- 

 FIG. 101 sanozoon. 



II. EXPERIMENTS ON PLANARIA TORVA 



1. The brain and nervous system of the fresh 

 water Planarian (Fig. 102, according to Jijima) 

 are so analogous to those of the marine Planarian, 

 that it is unnecessary for our purposes to give a 

 separate description of them. The most important 

 difference exists perhaps in the fact that the two 

 longitudinal nerves contain certain collections of 

 ganglion cells. One might think that the brain 

 function of the fresh -water Planarians might also be analogous 

 to those of the Polyclads. That is, however, not the case. 

 We experience here again what I have pointed out repeatedly 

 in my papers on the lower animals: that animals which are 

 very closely related morphologically may show the greatest 



FIG. 102 



