484 DAVENPORT HOOKER 
canal is being lengthened by the continuation of its lumen into 
this mass of cells is lacking, but the conformation of its supposed 
growing point and the nature of the canal:at the point of union 
in the completely reunited spinal cord is in favor of this 
supposition. 
Tadpole VIII 73 (fig. 8) is typical of those in which the restor- 
ation of the anatomical continuity of the cord is complete and will 
be described in detail as such. Four things only give internal 
evidence that the cord has been cut: 1, its slightly smaller diam- 
eter at the regenerated area, 2, the irregular course of the ca- 
nalis centralis, 3, the uneven distribution of cells and fiber-tracts 
Fig. 8 Sagittal section of an embryo killed 18 days after operation in which 
the spinal cord has completely regenerated. Note the ventral direction of the 
two portions of the canalis centralis shown. The original cut passed between 
them. (Embryo VIII 73, II 2-3). 
and 4, a deviation in the notochord which marks the site where 
it was severed. The skin and connective tissue lying above the 
cord have healed so completely that no indication of the original 
wound is given, unless it be a slight fold of the former. 
The regenerated area of the spinal cord has a diameter which 
at its most constricted point is 32u less than that of the cord on 
either side. From this narrowest region the diameter gradually 
_ Increases on both sides to that. of the normal cord. It is im- 
possible to accurately measure the length of the regenerated cord, 
as only in the center does it present any variations from the nor- 
mal structure. This region, however, is about 300, long. 
The canalis centralis of each end of the spinal cord bends 
ventrad to the point of juncture. For some distance on either 
