Wilson, Motor Endings of the Frog. 5 



The following investigations were undertaken by me to 

 determine how the motor nerve endings on the muscles of the 

 frog are related to other structures ; and also to ascertain, as 

 far as possible, how the terminal nerve fibrils finally break up 

 and disappear. Especially did it appear necessary to compare 

 the results observed by Ruffini and others using gold chloride 

 methods with the results obtained by the intra-vitam methylene 

 blue method. 



Method : The muscles of the frog used were either the M. 

 sartorius, the M. peroneus or the M. tibialis anticus. Into 

 these was injected with a hypodermic syringe, a very weak 

 solution of methylene blue in various salt solutions, for this re- 

 search has been carried on as a preliminary part of an investiga- 

 tion on the effect of various salts and poisons on motor nerve 

 endings. Grammolecular solutions of the following salts, among 

 others, were used : sodium chloride, sodium carbonate, sodium 

 ammonium phosphate, magnesium sulphate. Nerve endings 

 can be obtained by a solution of methylene blue in distilled 

 water, or with methylene blue in solution with any of the above 

 salts ; but the most constant and best results are obtained if 

 sodium chloride is present in the solution. So far as the pres- 

 ent paper is concerned, the following solution was constantly 

 employed: 



Methylene blue (Grubler's nach Ehrlich) o.^c;^ sol. i or 2 cc. 

 Sodium chloride solution, 0.58^ sol. 2 cc. 



Aqua destil. 17 cc. 



This was found to be the most suitable strength of methylene 

 blue to use, though one of half this strength often answers well, 

 especially for sensory endings and sympathetic plexures on blood 

 vessels. The largest and most complex endings were seen 

 when the muscle was injected with the above solution after 

 there had been added to it a few drops of a weak alkaline salt, 

 such as sodium ammonium phosphate, and then a very weak 

 faradic current passed through the nerve trunk for a i^w 

 seconds. 



A few minutes after injecting the solution the muscle is 

 cut out and exposed on a glass slide which has been moistened 



