No. 2.] CHANGES IN NERVE CELLS. 115 



is conducting impulses peripherally to its muscles, it may be 

 taken for granted that it is conducting impulses in like manner 

 centrally to its ganglion. 



In general, as a means of stimulation, the ordinary combina- 

 tion was used of Du Bois Reymond coil, platinum electrodes, and 

 bichromate or copper sulphate cell ; and the strength of stimulus 

 was determined within physiological limits by touching the elec- 

 trodes to the tongue before beginning to stimulate. For the 

 first few experiments the animal was put under the influence of 

 curare and the stimulation was continuous. Failing of any re- 

 sults, the use of curare was abandoned (39, p. 523) and intervals 

 of rest were allowed. At first this was managed by placing a 

 key in the circuit and making and breaking the circuit once a 

 minute by hand. In later experiments, this was relegated to 

 clockwork, which spaced the intervals with more precision and 

 removed the chief feature of irksomeness from the operation. 



At the end of the desired length of time, the stimulated 

 ganglion, with its mate of the opposite side, was excised as 

 quickly as possible and the process of fixing and hardening 

 begun. The method from this point on is directed toward 

 having the two ganglia pass through identical treatment. In no 

 instance were they separated from the time they left the animal to 

 the time when, placed side by side upon the same slide, they appeared 

 under the microscope for study. Not only were they carried through 

 the same reagents, but, in every case through the same reagents 

 in the same bottles or dishes from the first fixing fluid to the solid 

 paraffin. And further, the two are cnt at the same stroke of the 

 microtome knife, fixed to the slide together, stained together, and 

 appear side by side in the same field of the microscope. 



The carrying of a large number of specimens through the 

 hardening and embedding and cutting processes, keeping each 

 distinct, was greatly facilitated by the following simple device. 

 At first slips of mica were used, but a thin hard cardboard was 

 found to be more convenient. This is cut into strips, — 3 X i cm. 

 is a good size, — and the ganglia, which are carried up to strong 

 alcohol attached to their segment of the cord, are trimmed for 

 cutting and arranged, the two to be compared touching each 

 other, upon one end of the strip of cardboard. A drop of the 

 white of an egg is now placed over them, allowed to dry some- 

 what, and the whole carefully laid in alcohol. The albumen is 



