480 C. M. Child 



attaining some other position. In the case of a terminal or lateral 

 transverse wound, continued spiral inrolling of the cut margin of 

 the body-wall is impossible both because of mechanical conditions 

 in the wall (i.e., the region nearest the wound contracts most 

 strongly) and because of the presence of more or less voluminous 

 organs in the enteron. Moreover, as pointed out above, the mesen- 

 teries are important factors in bringing the cut margins together 

 in certain cases. In the case of longitudinal wounds, however, 

 none of these factors can serve to bring the margins together, con- 

 sequently closure of such wounds occurs only rarely. In the case 

 of short longitudinal wounds the mechanical conditions on the 

 body-wall prevent any great degree of inrolling, and the cut mar- 

 gins, especially near the ends of the wound, usually approach each 

 other sufficiently to permit the formation of new tissue and closure. 

 On the other hand, it is possible to induce experimentally 

 peculiar methods of wound closure and union of the cut margins 

 in such manner that anything like return to the usual form is 

 impossible. Such results can be attained simply by altering the 

 relations between the various mechanical factors involved in 

 approximation of the cut surfaces. One case of this kind, which 

 is of especial interest, will serve to illustrate the point. Pieces of 

 the body from the region between the lines c and d, Fig. 2, contain 

 the large retractor muscles and when contraction occurs after 

 isolation of the pieces (e.g., by two transverse cuts) parts of the 

 muscles and mesenteries usually protrude from one or both ends 

 of the piece (Fig. 14). In such pieces it is possible, with a little 

 care, to remove completely the retractor muscles and the parts of 

 the mesenteries in which they are imbedded. In this operation 

 two results important for the further history of the piece are 

 attained, viz: first, the mass of the enteric organs in the piece is 

 much reduced; and, second, the removal of the axial portion of 

 each mesentery leaves a longitudinal wound involving the whole 

 length of each mesentery (see the dotted lines in Fig. 14), besides 

 the transverse wounds made when the piece was isolated. In 

 these pieces the wounded edges of the mesenteries contract and 

 the result is the approximation o{ oral and aboral cut margins of 

 the body-wall and their union (Fig. 15). This method of closure 



