488 CM. Child. 



to change in position of cells from the old part. The removal of a 

 part leaves a more or less widely open wound and the soft tissues 

 of the body may gradually migrate or flow out in consequence of 

 altered conditions of surface tension or capillarity, or may be forced 

 out by internal pressure in consequence of muscular contractions 

 in the old part. The rounded form of this new tissue suggests the 

 possibility that surface tension may play a part in its formation. 

 At the same time it is probable and indeed certain in many cases 

 that rapid proliferation of the cells near the cut surface does 

 occur. This multiplication has been ascribed in a general and 

 somewhat vague manner to the altered conditions at the cut sur- 

 face, doubtless a correct conclusion as far as it goes. The possi- 

 bility that altered conditions of surface tension and pressure 

 resulting from the removal of the part which originally adjoined 

 the cut surface may themselves bring about multiplication has, 

 however, received little attention, although various experimenters 

 have shown that cell division is influenced by changes in these con- 

 ditions. Various other physical and chemical factors resulting 

 from the injury may also be concerned in this process, but the point 

 to which I desire to call especial attention is that the appearance 

 of new tissue from the cut surface is not primarily a regeneration 

 of anything in particular, but may be largely a flowing out of the 

 soft viscid contents of the body in consequence of reduced pres- 

 sure in this direction or altered conditions of surface tension ac- 

 companied by a more or less rapid multiplication of cells which is 

 itself the result of the actual conditions. In short the factors con- 

 cerned are local and are mostly present whether the parts are used 

 in a particular manner or not. The relative amounts of trans- 

 position and of proliferation doubtless differ widely in different 

 species according to their consistency and reactive capacity. 



If we admit that the first appearance of ''new tissue " from the 

 cut surface is determined by these relatively simple local factors 

 there is no obvious reason why in a given species the amount of this 

 new tissue formed from a cut surface at a given level in a given time 

 should not be approximately the same in different individuals, 

 whether the ganglia are present or not. The only way in which 

 the presence or absence of the ganglia might affect the result lies, 



