SPINAL CORD REGENERATION. II 425 
nearly or quite normal in behavior, a large proportion of them 
died. 
Each embryo, with its normal control, was placed in a sepa- 
rate Syracuse watch glass, was given an individual number and a 
separate protocol was kept for it. 
The embryos were mechanically stimulated at frequent in- 
tervals by lightly touching or brushing the surface of the body 
with a soft human hair, according to the method employed by 
Coghill (’09 et seq.). This method is very satisfactory, though 
it must be borne in mind that by poking the embryo even a 
human hair will penetrate the skin and directly stimulate the 
myotomes. 
The embryos were fixed at intervals of from twenty-four hours 
to eight days after operation in sublimate acetic, with the excep- 
tion of those that were to be used for the Bartelmez silver nitrate 
method, which were fixed in the absolute alcohol and acetic 
acid mixture. As the embryos developed very rapidly, the 
eight-day specimens were well advanced. 
Serial sections of the embryos were stained with Held’s molyb- 
die acid hematoxylin and congo red, Ehrlich’s hematoxylin and 
congo red, erythrosin and toluidin blue or the Bartelmez silver 
nitrate method. 
Wound healing. The method of healing a single, severing cut 
through the spinal cord has been described in detail in the first 
paper of this series.? A careful study of sections of the embryos 
with reversed portions of the spinal cord shows that, in the 
main, the method of healing is the same whether a piece of the 
cord be reversed or whether it be simply severed, but that 
in the former case the reversal brings in certain disturbing fac- 
tors which tend to mask and limit the processes at work. An 
embryo with the cord severed will, in the majority of cases, 
re-establish anatomical and functional continuity of the cord 
whether the wound surfaces heal per primum or not, but those 
embryos in which a piece of the cord was reversed rarely exhib- 
ited complete reunion of the cord, though this sometimes oc- 
3D. Hooker, 715, pp. 471-486. 
