650 TRANSACTIONS OF SECTION I. 
4. A Comparison of Naturally and Artificially aroused Impulses under 
the Influence of Nerve Blocks. By Cuartes M. Gruser. 
The research, of which a brief report is here presented, was begun by Dr. 
Hyde several years ago, at the suggestion of Dr. C. S. Sherrington, in his labora- 
tory in the University of Liverpool, and was completed by one of Dr. Hyde’s 
research students. 
It was conclusively proved by me that impulses aroused by artificial stimuli 
in a frog’s sciatic nerve can be suppressed by the tripolar electrical block, liquid 
air, and other blocking agencies, and that the tripolar block could be repeatedly 
introduced in the circuit without injury to the nerve’s function. Also that 
afferent impulses could be inhibited with weaker currents than could the efferent 
impulses. It was of interest, therefore, to ascertain whether natural impulses 
originated by higher centres in the brain were physically of the same nature as 
those electrically produced, and could be suppressed by the same kind and 
strength of block as could those artificially aroused by the electrical current. 
The experiments were conducted on the phrenic nerves in rabbits. By means 
of a modification of Head’s method, records of the movements of the diaphragm 
and the thoracic wall were obtained. The artificial stimuli were the threshold 
strengths of the faradic currents applied to the phrenic nerve and its branches ; 
the movements of the diaphragm in response to these stimuli and the contractions 
of the diaphragm resulting from the stimuli emanating from higher centres in 
the brain were recorded and compared. If the phrenic nerve or any of its 
hranches are stimulated with the weakest possible current, it is responded to, 
throughout the period, by a contraction of the diaphragm or an inspiratory phase 
of the side stimulated. The efficiency of the tripolar electrical block was com- 
pared with others, especially those produced by cocaine and freezing mixtures, 
and liquid air. 
It was found that the contractions of the diaphragm were suppressed the 
instant, and throughout the period, that the tripolar block circuit was closed. 
The strength of the block current was not more than (2.8)? volts, and this 
strength would suppress the cranial or naturally aroused impulses, as well as 
those originated by the very weakest faradic current. Only in one experiment 
did a block of (1:4)? volts inhibit the cranial, but not the artificially aroused, 
impulses. 
But cocaine, a freezing mixture of sodium chloride and ice, or liquid air, 
proved efficient in suppressing the impulses originated by the higher centres in 
ihe phrenic as well as those produced by electrical stimuli. But these blecks are 
inferior to the tripolar, because they cannot be repeatedly employed without 
injury to the function of the nerve. 
‘The presence of afferent fibres in the phrenic was well demonstrated by a 
simple experiment. When the motor impulses on one side were blocked, and the 
phrenic stimulated centrally to the block, a change in rate and amplitude of the 
diaphragmatic movements of the opposite side followed, as was indicated by the 
contraction curves secured from the diaphragm slips on that side. The same 
result was obtained when the phrenic of one side was cut and the central cut end 
stimulated, Stimulating or irritating the peritoneum in different regions of the 
abdomen with intact phrenic is followed by a change in rate and force of the 
respiratory movements. This is, however, probably due to afferent stimuli from 
nerves other than the phrenic to the respiratory centre. 
5. The Influence of Alcohol upon the Reflex Action of some Cutaneous 
Sense Organs in the Frog. By Professor Ipa Hypr, Miss R. 
Spray, and Miss I. Howat. 
A search of physiological literature reveals the fact that very little work 
has been done in regard to certain questions which form the basis of a research, 
a summary of the results of which I should like to present—namely, how soon 
after administering a minimal and also stronger doses of alcohol does a change in 
reflex time appear ?—that is, in certain neurons whose effects can be observed 
only under certain conditions. How long does the change last? when do the 
reflex actions cease? and for how long are they absent? When are the reflex 
times normal again? The experiments undertaken to investigate the problem 
EE 
