1910.] Reversal of the Reflex Effect of an Afferent Nerve. 439 
phase of the reflex often presents itself on the record as a mere spike 
ushering in and immediately followed by swift inhibitory relaxation. With 
faradic stimulation of moderate or strong intensity all trace of contraction 
usually disappears. 
(5) The difference between the effect of galvanic and faradic stimulation 
might obviously be referable to the more abrupt and momentary character 
of the latter. From our observations we received the impression that with 
stimuli still less abrupt than the make and break of the constant current as 
ordinarily performed, the contraction phase of the reflexes might be better 
developed. As a means for providing such stimuli we turned to the rotating 
rheonome of v. Kries. A description of this instrument is furnished by 
Metzner* (1893), who used it for stimulation of the frog nerve-muscle 
preparation in his research on work and heat output in muscle. It is 
essentially a key which rhythmically alternates the direction and varies by 
rectilinear increments and decrements the amount of galvanic current 
delivered through the stimulating electrodes. With two small modifications 
we have employed it in its original form, and with the slope of increment 
and decrement of current at less than the maximal steepness which the 
instrument permits. For comparing its effects on the preparation with those 
of faradic stimulation from the ordinary inductorium, we arranged our 
apparatus in the manner shown in the figure subjoined (fig. 4). The circuit 
was fed by one Leclanché cell. The speed of rotation generally used for the 
rheonome gave 20 stimuli per second. The electrodes were non-polarisable, 
of the du Bois Reymond pattern, and the distance between them on the 
afferent nerve was always about 1 cm. 
Like the serial brief galvanic currents simply made and broken, the 
galvanic stimulation given by the rotating rheonome produces reflex 
inhibition when the current is strong. But when the current is weak it 
produces reflex contraction, and as was anticipated the reflex contraction 
is more pronounced and more durable than with the other forms of stimula- 
tion we have used. By employing it we find reflex contractions of the 
extensor muscle obtainable which exhibit pre-eminently certain characteristic 
features. Among these features are peculiar slowness of development of the 
contraction, mild and steady intensity of contraction, long maintenance of 
the contraction without decline or interruption by fatigue or tremor, and slow 
subsidence of the contraction on terminating the stimulation (fig. 5). In fact 
with the stimulus which the rotating rheonome provides, we obtain extensor 
contraction reflexes of a characteristic kind. 
* Rudolf Metzner, ‘ Archiv f. Physiologie,’ 1893, Supplement-Band, p. 84. 
