600 REPORT—1899. 
their value. To do this it did not seem necessary, or even advisable, to 
confine the research to direct experiments upon the phrenic nerve, as it 
was presumed that errors (such as were sought for) would affect the appa- 
rent changes in any nerve under similar conditions of experiment to a 
degree dependent upon the vascularity of the nerve and the maintenance 
of its blood supply. 
Experimental means were obtained for the simultaneous record upon 
same travelling surface of the movements both of a galvanometer and of 
a blood-pressure manometer. In this way two curves were obtained, one 
of electrical changes in tissue experimented upon and one of blood pressure 
in general circulation, admitting of immediate contrast. 
The nerves chosen for experiment were :— 
(a) The central end of divided vagus. 
(b) The peripheral end of divided vagus, 
(c) The recurrent laryngeal. 
In all these cases phenomena were found characteristic of each indi- 
‘vidual nerve and irrespective of state of blood pressure, which will be 
elsewhere described. 
But in addition indications were obtained and records taken of a rela- 
tion sometimes existing between change of blood pressure and change of 
demarcation current in nerve, a fall of pressure being accompanied by a 
fall of current, and a succeeding rise of pressure by an increase in current. 
In such cases the parallelism of curves when obtained is of a crude 
description, the galvanometer record following the main trend of the blood- - 
pressure record, but not responding to the finer variations. It is also 
thought that such parallel curves are best obtained at the end of an 
experiment, when the nerve has presumably suffered from exposure. 
A somewhat similar comparison! has been made previously by other 
observers in the case of spinal nerves, in which the demarcation current 
was noticed as dependent upon the condition of animal. 
A very remarkable variation from such observations was, however, 
several times obtained from the peripheral end of divided vagus, in which 
the relation between the curves was inverted ; a rise of blood pressure 
being accompanied by a negative variation in demarcation current, a fall 
with an increase. There is also a marked difference in the nature of cor- 
respondence between the two curves from that previously related, in this 
case much more exact, finer changes being responded to and with a con- 
stant latency. 
The possible presence of a double relation of demarcation current in 
the peripheral end of vagus to changes of blood pressure, one in the oppo- 
site direction to the other, was naturally the cause of a multiplicity of 
experiments made upon this stretch of nerve. It might be remarked that 
whilst the first type of change is analogous to that so far found in other 
nerves, this second is peculiar to the nerve in question ; and although 
admitting of a simple explanation by the behaviour of electromotive 
changes in the walls of blood-vessels contained in it, is not (for reasons to 
be elsewhere advanced) thought to be so caused. 
In continuation of general research an attempt was made to differen- 
tiate between the secondary results of an altered circulation in nerve and 
' Gotch and Horsley, Croonian Lectures, 1891. 
