SPINAL CORD REGENERATION. I 489 
spite of this, the number of mitoses to be found is too small to 
account for the mass of cells produced. An explanation for this 
isnot at hand. A similar discrepancy between the number of 
mitoses found and the number of cells produced has been noted 
by Caporaso (’89) in the regenerating cord of triton. The 
position of the mass of proliferating cells indicates that any in- 
crease in the length of the canalis centralis and the consequent 
elongation of the cord stumps does not take place at the tip, 
but just behind it, by the interpolation of elements. 
After the cord has been restored both in structure and form, 
it contains all the essentials elements normally found in it, though 
the number of nerve cells is somewhat smaller. The regener- 
ation has been effected by the growth of a new piece of cord 
connecting the cut ends of the original one. The consequent 
increase in length is compensated to some extent by the sepa-. 
ration of the cord ends during the growth of the earlier stages. 
Nevertheless, the distance between the first pair of spinal ganglia 
in front of the cut and the first pair behind is increased by the 
original gaping of the wound. That the interposed area has 
developed entirely from the structures of the original cord is 
well assured. The only possible extraneous sources for the 
elements of the new section of the cord are the epidermis and the 
surrounding connective tissue. The first, probably, and the 
second, certainly, does not enter into the regenerative process. 
The absence of multiple central canals in the operated embryos 
is of interest in the light of previous investigation. Born (97) 
noted their presence in some of his composite frog embryos. 
Fraisse (’85) and a number of others have found the same con- 
dition in the regenerated tails of lizards. In a recent paper 
(14), Waelsch has attempted an analysis of multiple central 
canal formation in the chick, following the introduction of 
Scharlach R. in oil under the medullary plate. He concludes 
that the well known power of Scharlach R. to stimulate epithelial 
growth holds good in the case of the epithelial cells of the central 
canal, stimulating them to overgrowth which results in the 
multiplication of the canal. Weber (715), in commenting on 
Waelsch’s paper, attributes this phenomenon to any stimulus, 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 25, NO. 5 
