1912.] Contributions to the Histo- Chemistry of Nerve. 



123 



incubator at 37° C. The pieces were removed at the end of one, two, three, 

 four, and six days respectively, and fixed in 1-per-cent. osmic acid as 

 described above. 



Microscopical Findings. — The one- and two-day preparations showed few 

 changes, although in the latter some fibres were beginning to break up. 

 The three- and four-day preparations were distinctly changed. In many of 

 the fibres the myelin sheath was broken up and beaded, showed vacuoles 

 and irregular clumps of granular detritus. After six clays the changes were 

 very marked (see Plate 4, fig. 1). 



These changes strongly suggested the classical signs of Wallerian degenera- 

 tion as seen in nerves of living animals, following interruption of continuity. 



The experiment was repeated in another series, and the findings were very 

 much the same. Nerves were also kept in Einger's solution for longer 

 periods, up to 16 days, in order to see whether there would be a Marchi 

 reaction. In no case was a positive Marchi reaction obtained. 



Group II. — Comparison of Excised, Nerves Kept in Ringer s Solution at 37° C, 

 tvith Nerves Degenerated in the Living for Equal Lengths of Time. 



Cat «. — Under complete chloroform anaesthesia and with careful aseptic 

 precautions the right external popliteal nerve was freed, and a piece \ inch 

 long excised and placed in a Petri dish with sterile Einger's solution. 

 The wound was now closed. The Petri dish containing the excised piece 

 of nerve was placed in the incubator at 37° C. At the end of one day the cat 

 was killed and a piece of the peripheral stump of the divided nerve removed 

 and placed in 1-per-cent. osmic acid. The specimen in Einger's solution 

 was treated likewise, and both specimens run through for teasing and 

 embedding. 



By this means one could compare a specimen of a nerve degenerated 

 in vivo with another specimen of the same nerve kept in vitro for the same 

 length of time. 



Cats /3, 7, and 8. — Eepetition of the above, except that the lengths of time 

 between the excision and the removal of the peripheral stump ends were 

 two, three, and four days respectively. 



Microscopical Findings. — The specimens kept in Einger's solution presented 

 the same sort of appearance as those described under Group I. Very similar 

 to these changes were the changes to be observed in the specimens of the same 

 nerves which were actually degenerated in the living. 



There was, however, this difference. Although the degenerated fibres 

 were more or less broken up, and the myelin collected in elongated or round 

 masses, the stain was usually clear and well diffused. In the specimens 



