No. 3.] PERIPHERAL NERVES. 699 



assumes a black color, and is not touched by the safranin. 

 The same fact is observed during the early stages of degenera- 

 tion (myelin black and the protoplasm of a reddish tinge); as 

 degeneration proceeds, one sees that the myelin begins to be 

 stained also by the safranin, and now assumes a color which is 

 a mixture of the black and red stain. This change takes place 

 more rapidly near the nuclei. There is no marked increase of 

 the nuclei of the sheath of Schwann over that observed at the 

 end of the second day, although one finds now and then one in 

 mitosis, as is seen in PI. XXXIV, Fig. 2 b. The nuclei are 

 less numerous in a degenerating fibre of the implanted segment 

 than would be observed in degenerating fibres of the periph- 

 eral end at a corresponding stage. Polynuclear leucocytes are 

 found in large numbers in the endoneural connective tissue 

 between the nerve fibres at this stage (see PI. XXXIV, Fig. 2), 

 especially so in the outer portion of the implanted nerve trunk. 

 The fact that they are first observed in the epineurium, at a 

 little later stage in the lymph space between this sheath and 

 the nerve fibres, finally between the nerve fibres near the 

 epineurium, leads to the conviction that they wander in 

 through the connective tissue sheaths surrounding the im- 

 planted nerves. At this stage the endoneural connective 

 tissue cells are proliferating by means of mitotic division, as is 

 shown in PL XXXIV, Fig. 2 d. The peripheral portion of the 

 ulnar is up to this time of normal histological structure, and 

 stimulation with induction shocks excites contraction of the 

 muscles supplied. 



During the fourth and fifth days the fragmentation and 

 absorption of the myelin in the implanted fibres goes on quite 

 actively, yet not with the same rapidity in the diflFerent fibres 

 nor in different portions of the same fibre. The myelin would 

 seem to be absorbed more rapidly than the axis cylinders. In 

 longitudinal sections and teased preparations made from an 

 implanted nerve taken from a dog five days after the operation, 

 and stained in anilin blue, irregular segments of the axis cylin- 

 der, stained deep blue with the dye, are seen in nearly every 

 fibre. Some of these fragments are long, now and then 

 slightly twisted (see PI. XXXIV, Fig. 3 «), often ending in 



