428 DAVENPORT HOOKER 
of the invaginated epithelium. In this process of withdrawal, 
the epidermis maintains no epithelial connection with the cord 
by which it could play any réle in contributing elements to its 
regeneration. The mesenchyme cells slip in between the epi- 
Fig. 2 Condition at site of the wound twenty-four hours after operation. 
Epi, epidermis, which has grown down between the cut ends of the spinal cord 
and notochord; Mes, mesenchyme cells; Sp, spinal cord. Note the shght separa- 
tion on the left hand side of the figure from the epidermal ingrowth and the 
definite boundary of the neural cells. N, notochord. Note the large rounded 
cells at the cut edges which will proliferate to re-establish its continuity. Y, 
mesenchyme cells containing a large amount of yolk. 
This drawing is considerably schematized in order that the identity of the 
different cells may be more clearly brought out. As a matter of fact, the epi- 
dermal cells, shown lightly stippled in the drawing, are very similar to the 
neural cells, shown somewhat darker in the figure. Both contain a large amount 
of yolk, as do the cells of the notochord and the mesenchyme. The definite con- 
tinuity of the epidermal ingrowth and the rounded end of the spinal cord render 
identification of the cells possible. This figure represents the condition follow- 
ing the stage of primary repair of the wound. With further development the 
epidermal ingrowth will be withdrawn and the continuity of the two ends of the 
cord re-established. (Mmbryo VIII, 83.) 
