544' C. M. Child. 



intestinal branches grew into the new tissue more rapidly than 

 elsewhere and finally filled it almost as completely as in a normal 

 animal; some branches also extended from this region posteriorly 

 into the pharyngeal region; third, intestinal branches also ap- 

 peared in the new tissue posterior to the pharyngeal region but 

 somewhat later than those in the head region; these never attained 

 so great an extent as those in the anterior region but some ex- 

 tended anteriorly into the pharyngeal region. ^ 



These three features were, as stated, characteristic of all pieces 

 of this kind and must therefore possess a certain significance. The 

 first two, viz: the more rapid regeneration of the lateral regions of 

 the head and the more rapid growth of the intestinal branches 

 in this region are connected. In my opinion both are due to the 

 fact that this region shows the greatest motor activity of any part 

 of the body. Its characteristic activities have already been de- 

 scribed (Child, '04a). Characteristic conditions of tension and 

 pressure result from these characteristic movements and these are 

 undoubtedly factors in the arrangement of the material and so 

 in determining the form and may themselves constitute stimuli 

 to growth. As regards the intestinal branches the internal pres- 

 sure due to intestinal contents must undergo change with the 

 movements as the fluid is forced into or out of the branches as 

 contraction or extension occurs. In the head-region the internal 

 pressure in the peripheral branches of the intestine is greater than 

 in other parts, /. e., the contents are forced into these branches 

 more frequently and probably also with greater pressure than 

 elsewhere. Brief observation of a specimen with well-filled in- 

 testine is sufficient to demonstrate these facts very clearly. There 

 can be no doubt that these conditions of internal pressure play a 

 part in the development of the intestine; some experimental 

 evidence upon this point has been obtained from study of another 

 species; this I hope to present at another time. Admitting that 

 the internal pressure is a factor in the development of the intestine 

 it is easy to see that the same conditions, viz: greater functional 

 motor activity, which bring about the more rapid regeneration 

 in the anterior region also bring about the more rapid growth ot 

 the intestinal branches in this region. 



