670 A. “f. Goldfarb 
motor reactions indicate very clearly that the whole of the cord 
within the plexus region had not been destroyed, for, in my experi- 
ments permanent paralysis followed this operation, and when a 
minute part of the cord was left in the plexus, the limb sooner 
or later displayed some movement. ‘The presumption is then that 
in Wolff’s experiments some motor stimuli were transmitted to the 
limb, from the very beginning or soon thereafter. It 1s thus highly 
probable that only a part, perhaps the major part, of the nerve 
stimuli had been withdrawn from the limbs in his experiments. 
Because most of the limbs whose nervous supply has been par- 
tially removed had a reduced number of toes, Wolff was led to 
adopt the view that the nervous system exerted some influence in 
regeneration. But what is the nature of this influence ? 
Does the removal of the nervous system remove from the limb 
certain morphogenetic stimuli, thereby preventing the forma-. 
tion of new structures, or»does its absence cause injurious 
secondary conditions such as changes in blood supply and there- 
fore of food and oxygen, accumulation of excretory products, the 
degeneration of the musculature and other tissues, etc., and thus 
indirectly affect the regeneration of the limb? ‘That loss of nerve 
stimuli brings these injurious conditions about 1s well known. 
That it should tend to the formation of incomplete or malformed 
organs during regeneration is no more to be wondered at than that 
malformed structures should result from injuries not directly in- 
volving the nervous system or from the use of various chemicals in 
embryonic development. The morphogenetic processes go on in 
the absence of nerves, and in spite of the adverse conditions, as 
witnessed in the normal differentiation of cartilage, muscles, etc., 
of the leg, foot and tail. The surprising thing is not that organs 
are sometimes atypic, but that regeneration should take place at all 
under the circumstances. 
Regeneration of the Tail after Removal of the Nerve Cord 
Diemyctylus, like other newts and salamanders, readily regener- 
ates its tail. About twenty-five days after the amputation, the 
time varying largely with the temperature, the bud of the new tail 
