STUDIES ON REGENERATION IN THE SPINAL CORD 
I. AN ANALYSIS OF THE PROCESSES LEADING TO ITS REUNION 
AFTER IT HAS BEEN COMPLETELY SEVERED IN FROG EMBRYOS 
AT THE STAGE OF CLOSED NEURAL FOLDS 
DAVENPORT HOOKER 
Anatomical Laboratories of the University of Pittsburgh School of Medicine, 
Pittsburgh, Pa. 
EIGHT FIGURES 
In 1913! a systematic study was begun on the restoration of 
anatomical and physiological continuity of the spinal cord 
severed at different ages. To the present time experiments have 
been carried out on three series of frog embryos and tadpoles 
and further work is being done on later stages. The object of 
this study is to obtain evidence which will aid in clearing up 
the conflicting results of previous investigations and especially 
to determine the following points: 1, whether the completely 
severed spinal cord will regenerate; 2, the nature of the process, 
if healing occurs; 3, the causes which prevent it, if it fails; 4, the 
origin of the regenerated elements and whether the epidermis 
or connective tissue play any role; 5, the effect of isolation of a 
segment of the cord upon. the development of reflexes in it in the 
early embryo, and 6, the physiological phenomena associated 
with the regeneration. 
Born (97) demonstrated that complete reunion of the severed 
spinal cord could easily be obtained in the frog embryo at the 
earliest neural tube stage provided the surfaces of the wound 
! The experiments described in this paper were carried out in the Anatomical 
Laboratory of the School of Medicine of Yale University. I take great pleasure 
in thanking Prof. H. B. Ferris for extending to me the courtesies of his labora- 
tory for this purpose. I am indebted to the Loomis Research Fund of the 
Yale University School of Medicine for some of the apparatus used. 
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