482 C. M. Child 



of wounds; 'o4d, wound closure in oesophageal pieces; '05a 

 formation of lateral mouths). 



2 The (Esophagus 



In the oesophageal region the oesophagus and the mesenteries 

 supplement each other: the walls of the oesophagus constitute one 

 of the points of attachment of the mesenteries, and the contrac- 

 tion of the latter draws the cut margins of oesophagus and body- 

 wall together. Both are essential factors in the result, viz, the 

 union of the cut edges of oesophagus and body-wall. Figs. 7-12 

 and Fig. 13, together with the explanations of these figures in the 

 preceding section, will suffice to make clear the relations of parts. 



5 Mass Effects of the Enteric Organs 



The mesenteries, with their large longitudinal muscles and 

 mesenterial filaments constitute a mass of considerable size in the 

 post-cesophageal region of the enteron. In most cases of section 

 of the body in regions between the aboral end of the oesophagus 

 and the attenuated region, i.e., between c and ^Fig. 2, the contrac- 

 tion following the wound is sufficient to force the mesenterial 

 organs out through the cut end to a greater or less extent, where 

 they form a plug which often delays or prevents closure of the 

 wound or in other cases becomes infected and frequently brings 

 about the death of the whole piece. In pieces with cut ends both 

 orally and aborally (Fig. 14) the mesenterial organs often protrude 

 from both ends, and such pieces are absolutely incapable of clos- 

 ing and undergoing regulation. The effect of removal of these 

 organs, i.e., the formation of " rings " (Fig. 15), was discussed above. 

 If the organs are not removed the extruded portion is sometimes 

 gradually constricted off from the remainder by the continued 

 contraction of the cut end of the body-wall about it. If the exter- 

 nal decaying portions do not infect the rest of the piece before they 

 separate regulation proceeds in the usual manner after the plug 

 has dropped off. On the other hand, in some cases, especially 

 when the piece is intact aborally, more or less elongation usually 

 follows the extreme contraction produced by the wound, and in 



