6 Journal of Comparative Neurology and Psychology. 



with normal salt solution. Within a varying time, usually 

 about five minutes, the nerve endings begin to appear. As 

 soon as these are well marked the muscle is fastened to cork 

 and placed in ammonium molybdate solution (5%) at a tem- 

 perature near freezing point. Temperature plays a very im- 

 portant part in the subsequent treatment of the tissues. If it 

 rise at any point of the procedure — e. g. when washing in 

 water or passing through alcohol — the methylene blue dissolves 

 out from the very fine fibrillae. If the tissue has to kept over 

 night in molybdate it is well to place it, especially in summer, 

 in a refrigerator. When passing through alcohol, the vessel 

 should be surrounded by ice-cold water. 



The addition of HCl to the molybdate solution is not nec- 

 essary ; I have found it even a disadvantage for the finer results. 

 Bethe in his recent work has abandoned its use. 



After removal from the molybdate, the muscle, if too thick, 

 is cut in a freezing microtome, examined in water, and only that 

 part kept which shows traces of nerve endings. The tissue is 

 now passed through 95 ^ and absolute alcohol, preferably, as 

 stated above, at a low temperature; then from xylol into par- 

 affin. It is important that it remain sufficiently long in xylol 

 to remove the alcohol ; otherwise the temperature of the melted 

 paraffin will cause any alcohol present to remove the methylene 

 blue from the fine fibrillae. It remains in paraffin for two 

 hours. The thickness of the section varies with the object 

 aimed at. To get long stretches of nerve endings, it is best to 

 cut from 20 to 50 micra ; if one wish to study the relation of 

 the endings to the muscle cell, a thickness of from 5 to 10 

 micra must be used. 



After numerous experiments with various dyes as a coun- 

 terstain, the following was found most suitable, inasmuch as it 

 dyed the muscle fiber an orange, the sheath of Henle a rose- 

 pink and the neurilemma a faint pink : 



