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ON ELECTRICAL CHANGES. 599 
Electrical Changes accompanying the discharge of the Respiratory 
Centre. Report of the Committee, consisting of Dr. A. WALLER 
(Chairman), Professor H. WaymMoutH Rep (Secretary), Professor 
F. Gorcu, and Mr. J. 8. Macponatp. (Drawn up by Mr. J. 8. 
MACDONALD.) 
Further Examination of Changes in Phrenic Nerve and their 
comparison with Simultaneous State of Blood Pressure. 
Tue further prosecution of research has taken the form of an inquiry 
into the nature of part (if any) played by alterations of blood presswre in 
the causation of electrical phenomena observed in the phrenie nerve. 
In a nerve well supplied with blood-vessels, and with a circulation 
preserved in such good condition as that noted in experiments, errors 
might be introduced by such alterations in several ways. 
(A) By alteration of volume of blood and lymph in nerve, and so of 
conducting media external to electrically disturbed tissue.' 
By such means a change, produced in the relative proportion of current 
derived through galvanometer circuit, might in records give rise to an 
apparent change of total current. 
(B) By action of changes of blood pressure upon the walls of vessels 
or upon the flow of blood through them, setting up electromotive changes 
of entirely different origin from intrinsic changes in nervous tissue. 
(C) By direct effect of alterations of circulation upon the nervous 
tissue itself, especially in nerve partially dried and cooled from exposure, 
giving rise to intrinsic alterations in current of injury by altering condi- 
tions of moisture, temperature, presence of waste products, &c., affecting its 
development. 
There were considerations which made it improbable that such causes 
were at work in the production of current changes observed in phrenic 
nerves. Amongst these may be mentioned— 
(1) The constancy of base line in tracings. 
(2) The character of the rhythmical oscillations, the first part of each 
of which bore evidence of being a true negative variation ; the second part, 
as observed both in galvanometer and electrometer, being due to return of 
instrument to rest at a rate determined by instrumental elasticity. 
(3) The observation that phenomena in phrenic ceased when blood 
pressure was still considerable, and the heart continued its beat. 
It was, indeed, anticipated that the relation between circumstances was 
really in a reverse order. That the phenomena, being genuine indications 
of large discharges from respiratory centre, would probably, in their most 
extreme form, be accompanied by discharges of vasomotor centres leading 
to alterations of blood pressure; and not that such indirectly caused 
changes of blood pressure would declare themselves so obviously by 
indirect effects upon injury current of phrenic nerves. 
It was, however, deemed advisable to satisfy any criticism upon pre- 
sence of errors of this nature by as careful as possible an estimation of 
} Source of current of injury. 
