No. 2.] CHANGES IN NERVE CELLS. 133 



mercury every minute. By placing the cup upon the head of a 

 screw, so that the mercury can be raised and lowered at will, 

 and by proper shaping of the eccentric disc, it is easy to so 

 adjust it that the circuit is made through the mercury fifteen 

 seconds and broken forty-five seconds, which is the spacing of 

 intervals desired. The whole is arranged upon a small board, 

 into which two binding screws are set for convenience of joining 

 up with the circuit. This is, of course, placed in the primary 

 circuit. 



By this arrangement it was possible to control stimulation 

 quite accurately. A half ampere, as read from the galvanometer, 

 was used throughout the series. The automatic make and 

 break key gave regular intervals of rest and stimulation. The 

 beat of the interrupter was kept at twenty per second. The 

 secondary coil was set at a certain place and moved up at regu- 

 lar intervals, in the same manner for all the experiments. 



The animals used were a lucky lot, five gray kittens six or 

 eight weeks old, and as much alike as peas in a pod. Nothing 

 was fed after the commencement of the experiment, but up to 

 that time they were so well fed that it was thought a fast of 

 eleven to thirty hours would not complicate matters seriously, 

 if at all. The operation was made in every respect according to 

 the description already given. Stimulation was continued for 

 five hours in each case. The animal was then gently removed 

 from the holder, wrapped up, and laid in a warm place, where it 

 was left to sleep the desired number of hours. At the expira- 

 tion of this time the ganglia were cut out as quickly as possible. 

 The ist thoracic and 8th cervical pairs were used and were hard- 

 ened respectively in one per cent osm^c acid and saturated 

 mercuric chloride solution of 40° C. The precautions regarding 

 exactly similar treatment were the same as described for the 

 preceding series, and the cells and nuclei were measured and 

 dealt with by the method of arithmetical means as before. 



As there is often reason to distrust averages, I will give the 

 actual figures as they occur in a sample sheet of my notes 

 taken at random. The measurements were made with a Zeiss 

 eye-piece micrometer ruled to \ micron divisions (eye-piece 8 ; 

 objective 4.0 mm. x 500), hence each division equals 2|/Lt. They 

 are given, as read, in units of the micrometer. 



