46 CECIL SHEPAKD HIKES. 



Later I operated upon at least thirty salamanders in several 

 lots. Some of these were starved while others were well fed. 

 The abundance or lack of food did not seem to be a factor in the 

 rate of regeneration. Salamanders which were reduced almost 

 to "skin and bones" showed the same comparative amount of 

 regeneration as well-fed individuals. The influence of food did 

 show itself, however, in the amount of material proliferated. 

 During starvation an individual shrinks greatly in size and pro- 

 liferates much less material for the same relative amount of 

 regeneration as a well-fed companion. 



To ascertain whether the blood supply was a factor in regen- 

 eration the artery of several individuals was cut just above its 

 entrance into the leg, the nerve being left intact. The result 

 showed that the leg regenerated at the normal rate. However, 

 not much stress can be laid upon this experiment, owing to the 

 rapidity with which a sectioned blood-vessel heals. 



That the circulation in the leg may have continued to some 

 extent after the operation in those individuals whose nerve as 

 well as artery had been sectioned near the backbone was shown 

 conclusively by the following experiment. A salamander was 

 taken and a cut made in the pelvic region as before. Then a 

 vein was severed in the lower part of the leg. This continued 

 to bleed freely for a considerable time, as would not have occurred 

 had the total blood supply been cut off. The collateral blood 

 supply probably still brought blood to the limb. Similarly the 

 collateral nerve supply may in the first series of experiments 

 have sufficed to keep the regeneration up to the same rate as in 

 a limb in which the nerve was not cut. 



In a number of cases regeneration did not set in at all on the 

 side on which the nerve had been cut. At least, after a period 

 of two months and a half there was not the least sign of prolifer- 

 ation, while in the normal course of regeneration the new part 

 appears in about twenty-five days. This lack of regeneration is 

 probably due to the distal end of the nerve being displaced, and 

 in consequence the regenerating nerve was unable to grow down 

 its old path along the degenerated nerve, but was turned aside. 

 Consequently not even a retarded regeneration occurred. 



The most important work bearing on the question of the rela- 



