424 Mr. W. L. Symes and Dr. V. H. Veley. _— [Dee. 10, 
stimulation. With inductorium B, a block with the secondary coil at 
400 mm. was always complete at 300 mm. and at 200 mm., though not 
always at 100 mm., and when not so, was noticeably less effective against 
tetanisation than against single stimuli. In such cases, prolongation of the 
drug bath was necessary to abolish response with the secondary coil at zero. 
On substituting normal saline for the anesthetic solution, when the block 
is complete, response remains for a time in abeyance, but sooner or later 
returns. 
The rate of recovery of the nerve is affected by the factors that influence 
the onset of the block. Increase in concentration of the drug, early 
repetition of the drug bath, and pronounced fall in temperature, all lead to 
delayed recovery, whilst a fresh nerve recovers (as it fails) more rapidly than 
a stale one. 
Furthermore, recovery is delayed by prolonging the duration of the drug 
bath after response has ceased. 
IV. EFFECTS OF THE INDIVIDUAL DRUGS. 
Cocaine Hydrochloride. 
In comparison with stovaine and its homologues, cocaine hydrochloride 
blocks somewhat less rapidly and allows much more rapid recovery. More- 
over, it is the most conspicuously affected by dilution, N/500 (0:07 per cent.) 
solutions acting with extreme slowness (Table I). 
Table I.*—Cocaine Hydrochloride. 
Time required to 
| 
| | 
; | : | Duration of 
Concentration. Temperature. block maximal | 
| 5 block. 
stimulus. | 
2. | mins. mins 
N/100 (0 ‘34 per cent.)......... 18 2 2 
a jc). Ue 10 6°5 15 
IN BOQ) eit other ee 18 2 <1 
ret CURA Peer PERRET rei baa 20 1 <1 
99 «Reo heOH OO E EOE cea edcreeree 20 1 3 DS 
IN BOO eset iatenceataenetn 18 °5 22 <1 
18 ‘5 53 <1 
Grost has shown that addition of sodium hydrate to a solution of cocaine 
hydrochloride accelerates its effect on the excitability of nerve, and attributes 
this to liberation of some of the cocaine base. In agreement with his, 
* In this and the following tables second and subsequent observations on the same 
nerves are not included. 
t+ Gros, ‘Archiv f. Exp. Pathol. u. Pharmakol.,’ 1910, vol. 63, p. 80. 
