1912.] Contributions to the Histo- Chemistry of Nerve. 125 



Knowing the effects of Einger's solution on nerve fibres, the question arose 

 whether the fluid constituents of the blood would have the same effect. This 

 experiment was carried out in the ice box, in order to exclude the effect of 

 bacterial contamination. 



Group V. — Comparison of Excised Nerve kept in Ice Box for Sic: Days in 

 Pdngers Solution with Excised Nerve kept in Blood Serum tinder Similar 

 Conditions. 



Cat chloroformed and external popliteal nerve removed under sterile pre- 

 cautions. The nerve was divided into two pieces and temporarily laid in a 

 sterile dish. The carotid artery of cat opened under sterile precautions, and 

 some blood allowed to flow into a Petri dish. The blood was allowed to clot 

 and the dish then tilted so as to cause the serum to flow to one side. The 

 one piece of nerve was laid in this serum, and the other was laid in a Petri 

 dish containing sterile Einger's solution. Both dishes were placed in the 

 ice box. Pieces were removed at the end of six days and fixed in 1-per-cent. 

 osmic acid. 



Microscopical Findings. — Both specimens showed the changes described 

 under Group I. The changes were about equal in amount. 



One of the essential differences between the conditions of a nerve degenerat- 

 ing in vivo and a nerve kept in vitro is the presence in the former of a 

 circulatory mechanism, which not only supplies the fibre with nutriment, 

 but in this case may also have an effect in removing products of degeneration. 

 In order to estimate the part played by this factor it was necessary to study 

 the changes in a nerve kept in vivo in the absence of any circulation. This 

 condition was obtained by tying a nerve in two places as described in the 

 following group. 



Group VI. — Nerves tied in Two Places in Living Cats. Comparison of Prepara- 

 tions made from the Segment between Ligatures with Preparations taken 

 from Segment below Lower Ligature. 



Under complete chloroform anaesthesia external popliteal nerve freed and 

 tied very tightly with catgut ligatures in two places f inch apart. 



Cat killed five days later. External popliteal nerve freed again. The 

 portion of the nerve between the ligatures shrunken to about one-half its 

 normal size. The portion below the lower ligature was somewhat swollen. 

 Pieces from between the ligatures and from below the lower ligature fixed in 

 1-per-cent. osmic acid. 



Microscopical Findings. — Preparations made from the segment below the 



