648 A. fF. Goldfarb 
ing the nerve cells. “This method is free from the first and second 
objections and, as will be later seen, from the third also. Its 
value depends on the certainty that all the nerve cells supplying the 
leg as well as the nerve cells for a considerable distance in adjacent 
regions are removed, and on the fact that no regeneration of new cells 
occurs during the period required for the formation of the limb. 
‘The animals were operated on as follows: ‘The tail was first 
amputated near its base. Then a fine needle or glass capillary or 
most often a dentist’s broach, technically known as a “ pulp-canal 
cleanser,” was introduced into the vertebral canal to any desired 
depth, to and beyond the lumbo-sacral plexus. ‘The contents, 
including the spinal cord, its membranes, the roots, etc., were 
destroyed by repeated movements of the instrument, and the débris 
withdrawn. One or both hind legs were then amputated. In this 
way the motor cells supplying the tail and the hind legs are effectu- _ 
ally removed. ‘This is evidenced by the complete paralysis of 
the legs, which after successful operations remained so for over 
nine months. Even the strongest stimuli failed to produce any 
reaction. ‘The muscles of the leg lose their tonus, and become 
considerably shrunken. The muscles of the bladder were like- 
wise paralyzed. The animals ate well and were otherwise in 
apparently good condition. 
About one month after the operation, the time varying with the 
season of the year, the new leg became visible in both normal and 
paralyzed individuals. The regeneration in the latter was some- 
what retarded. Any severe injury, as will later be shown, whether 
involving the nerves or any other tissue, retards regeneration. 
This is partly proven by the following: In control animals the 
regenerated fore leg appears usually a few days before the regener- 
ated hind leg, though both had been amputated at the same time 
and at the same level. ‘This slight lead is usually maintained 
throughout succeeding differentiations. When the hind leg 
developed first, the lead was sooner or later lost; the fore leg catches 
up or advances beyond the other. In paralyzed animals a longer 
period usually intervenes before the appearance of the new fore and 
hind legs. Once begun, however, the relation of the paralyzed 
hind and the non-paralyzed fore leg is exactly like that in the 
control animals. 
a eee 
