Studies on Regulation 375 



reaction is greater in proportion to that of the prepharyngeal reac- 

 tion, when the gangUa are absent, than when they are present. 



In such prepharyngeal pieces without the gangha the lateral 

 intestinal branches in the region posterior to the new pharynx dis- 

 appear in exactly the same manner as in the pieces already de- 

 scribed, though apparently somewhat more slowly. The absence 

 of the ganglia, therefore, does not affect intestinal regulation in 

 these pieces, except somewhat as regards rapidity. 



The products of degeneration of intestinal cells never accumu- 

 late to any great extent in these prepharyngeal pieces. Appar- 

 ently they undergo resorption almost as fast as they are formed, 

 serving, doubtless as nutritive material for the various regulatory 

 processes, and all parts of the intestine become more and more 

 slender and delicate as time goes on. 



b In the Postpharyngeal Region 



The character of intestinal regulation after removal of a part of 

 the postpharyngeal region differs according to the relative length 

 of the part removed. If the level of section lies only a short dis- 

 tance posterior to the old pharynx, e. g., at the line g, Fig. i, the 

 intestinal changes which occur in the region posterior to the old 

 pharynx are essentially identical in character with those described 

 for prepharyngeal pieces and shown in Fig. 7 and 8. This region, 

 originally the anterior end of the postpharyngeal region, rediffer- 

 entiates into a whole postpharyngeal region, and the lateral intes- 

 tinal branches disappear in the same manner as in pieces where the 

 postpharyngeal region is formed from a part of the prepharyngeal 

 region. One important difference exists, however; the degener- 

 ation is always less rapid in these than in prepharyngeal pieces, 

 from three to four weeks being necessary for the disappearance of 

 the branches. 



Similar changes occur in pieces with posterior ends at levels 

 somewhat posterior to g in Fig. i, but with increasing length of 

 the old postpharyngeal region in the piece, the degeneration of 

 the lateral branches becomes slower and less complete, until, 

 when half (/?, Fig. i) or more of the old postpharyngeal region 

 remains, the lateral branches do not disappear early as in the 



