68 ELBERT CLARK 



16, 19, 21 and 30 days respectively. The fowl which had been 

 kept for 30 days on the nutritive diet showed marked improve- 

 ment. In addition to nerves from this series, segments of the 

 sciatic, cut out from fowls 48, 56, 59 and 60 days in regeneration 

 respectively, were examined for embryonic nerve fibers and multi- 

 plication of the nuclei of the neurilemma sheath. These four 

 fowls had just become able to walk again. In neither teased 

 nor sectioned preparations of the nerves of all these fowls were 

 embryonic nerve fibers to be found. Nor was there observed 

 a more definite indication of multiplication of the nuclei of the 

 neurilemma sheath than was seen in the nerves of those fowls 

 killed at the time paralysis developed. This lack of nuclear 

 multiplication also obtained in nerves of fowls 108, 125, 171 and 

 275 days in regeneration. 



Attempts to produce by other means a degeneration in the 

 medullated fibers without a multiplication of the nuclei of the 

 sheath of Schwann were not successful. Freezing a small por- 

 tion of the sciatic with carbon dioxide snow, treating a portion 

 with chloroform vapor, and injecting a drop or two of chloro- 

 form into the nerve, when successful in producing degeneration, 

 resulted also in the typical and rapid increase in the nuclei of 

 the neurilemma sheath as has been constantly described after 

 section or hgature of the nerve. Less violent means were then 

 adopted in that rubber bands, tight enough to cut off the circu- 

 lation but not tight enough to do mechanical injury to the nerve 

 were placed around the thigh of fowls. Loss of control of the 

 leg resulted after 3 or 4 days, both when the bandage was allowed 

 to remain for 24 hours at a time and when it was on and off 

 every few hours over a course of 2 or 3 days. Although by this 

 method the result sought for was not accomplished, yet another 

 observation of equal importance was made. Fowl No. 78, on 

 which the bandage was allowed to remain for 24 hours, experi- 

 enced considerable oedema of the bandaged leg; this condition 

 progressed, without infection, to dry gangrene of nearly all of 

 that portion peripheral to the bandage by the twenty-eighth 

 day, or approximately 24 days after loss of control of the leg. 

 This, then, represents a nerve in which only retrogressive changes 



