No. 3.] PERIPHERAL NERVES. 637 



ever, of the opinion that the elements of the transplanted nerve 

 furnished the material for the newly formed fibres. He traces 

 the development of the new axis cylinders from the mitotically 

 increased nerve nuclei and proliferated protoplasm of the sheath 

 of Schwann belonging to the nerve fibres of the implanted seg- 

 ment. Before dissenting from Biinger's interpretation of this 

 experiment, it is necessary and just to explain what his position 

 is concerning degeneration and regeneration of divided nerves. 

 In the first place, he states that there is no time interval sep- 

 arating degeneration and regeneration ; regeneration begins 

 soon after the former is initiated, and goes on while degeneration 

 is drawing to a close. 



In the guinea pigs used for experimentation the axis cylinder 

 and myelin disintegrate soon after injury to the nerve. At 

 the beginning of the^third day the nuclei of the sheath of 

 Schwann begin to divide karyokinetically, and at the same time 

 a proliferation of the protoplasm is noticed. The increase of 

 the nuclei and protoplasm marks the beginning of the regen- 

 erative process. This increase continues while the myelin and 

 old axis cylinders are degenerating. Toward the end of the 

 second week the proliferated nuclei begin to arrange themselves 

 in one or two (very seldom more) rows, parallel to the long axis 

 of the nerve ; and the protoplasm, which up to this time has 

 been homogeneous, begins to be longitudinally striated. " The 

 fibrillar striation is the anlage of the new axis cylinder, and is 

 developed from the protoplasmic contents of the nerve fibres." 

 This is first observed near the wound. By the end of the sec- 

 ond week the new axis cylinders have developed centrifugally 

 some distance away from the seat of injury, and are richly 

 beset with nuclei. In the third week a thin continuous layer 

 of myelin surrounds the axis cylinder. Later another sheath 

 of myelin developing in segments blends with the continuous 

 sheath. The nerve fibres developing in the periphery unite 

 with newly formed fibres, which have their origin in pro- 

 liferated nuclei and protoplasm of the peripheral end of the 

 nerve fibres in the central nerve stump. These observations 

 were made on degenerating and regenerating nerves hardened 

 in Flemming's solution and stained in safranin, a method 



