172 



Dr. K H. Alcock. The Electromotive [Dec. 15, 



These tables show very clearly the alteration in the negative varia- 

 tion by successive excitations. The decrease is most rapid at first, 

 and after a little proceeds quite slowly, especially if the excitation 

 is sub-maximal, so that if the result of the first few minutes is dis- 

 carded, there remains a considerable period during which the diminu- 

 tion is small, and which can be used to test any desired procedure 

 (vide figs. 1 and 6). The effect of rest is that the subsequent responses are 

 greater for a time, but soon fall off (fig. 1), and the difference in this 

 respect from the medullated nerves is very marked (fig. 2); in the 

 latter the subsequent negative variations are almost invariably less 

 after a pause. 



This difference is very clearly seen in the electrometer photographs 

 (Experiment 750, B, fig. 3, splenic of horse, and Experiment 751, fig. 4, 



^•ooi volt. 



Fig. 3 (Exp. 750, B,). — Non-medullated Nerve, Splenic of Horse. Excitation for 

 10 seconds (Tet.), interval£20 seconds, as shown by the lower interrupted line. 



Time— 1 mm. = 2 seconds. 



Fig. 4 (Exp. 751).— Medullated Nerve, Ulnar of Cat. Details as in Fig. 3. 



