NERVE CUTTING IN AMIURUS 387 
touched without eliciting any response from the fish. There 
was no effect whatever, if the experiment were carefully per- 
formed, whether a glass rod, a steel rod, or a piece of worm was 
used. If, on the contrary, the uninjured barbels on these same 
fish or on normal fish were treated in this manner, the fish either 
nibbled at the worm and rods or moved away from the rods in 
a perfectly normal manner. ‘The barbels, therefore, whose nerves 
had been cut, were lacking in both the sensation of taste and of 
touch. These physiological tests were appled from time to 
time, but no attempt was made to stimulate any special region 
of the barbel, for I did not know at the time of this experiment 
that regeneration at the base of the barbel begins in less than 
three weeks and progresses toward the tip at the rate of almost 
a millimeter a day. Forty days after the operation the fishes 
behaved altogether normally, all their barbels being sensitive 
alike to the glass and steel rods and to the worm. To be abso- 
lutely certain, eight days more were allowed to elapse before 
removing and preparing the denervated barbels for histological 
study. Eight barbels from two fish were prepared and all of 
them were found to be perfectly normal as regards taste buds 
(fig. 16). The nerve in transverse section showed division into 
fascicles as in normal barbels, thus contrasting with the condition 
at fifteen days in figure 28. Longitudinal sections showed the 
characteristic fibrillar structure of normal nerve. At the end 
of sixty days the remaining twelve barbels were cut. All of 
these were found to be entirely normal. In twenty barbels, 
therefore, there was complete regeneration of nerves and of 
taste buds within two months after the cutting of the nerve. 
This proves that not only does degeneration of the taste buds 
follow degeneration of the nerve, but regeneration of the nerve 
is accompanied by regeneration of the taste buds, and the cycle 
is complete. 
REGENERATION OF WHOLE BARBELS 
It was noticed that on fish whose barbels had been completely 
removed, either with or without having had the nerve cut, there 
appeared after four weeks tiny new barbels 1 to 2 mm. in length. 
