1889.] Physiology. 831 
skull. The central branch of this ganglion is of sufficient length to 
allow stimulation ; the peripheral branch, the vagus nerve, has the 
great advantage that its functions are well known. The effects which 
cutting of the central and the peripheral branches and the consequent 
degeneration have upon both the structure and function of the nerve 
fibres of the vagus were studied, together with the time occupied by 
the passage of the nerve current through the ganglion. The authors 
feel justified in drawing the following conclusions from their work : — 
Most centripetal nerve paths are interrupted in the spinal ganglia by 
bipolar nerve cells. The function of these nerve cells is to exercise a 
trophic influence over the nerve fibres joining them. For the mainten- 
ance of the normal structure and function of centripetal nerve fibres 
connection with the spinal ganglia is necessary and sufficient. Every 
excitation wave of a centripetal nerve fibre must pass through a nerve 
cell in the spinal ganglion. Whether the difference of time in the 
reaction from stimulating peripherally and centrally from the 
ganglion is due to retardation of the nerve current in its passage 
through the ganglion, or to a special summation of subminimal stimuli 
there taking place, is uncertain. (The former time was .036 sec. 
longer than the latter, the centripetal fibres being stimulated and the 
reaction being the effect on the respiration movements.) The loss of 
function of both centripetal and centrifugal nerve fibres that have 
been separated from their trophic centres is fully developed in animals 
at the end of the second or the beginning of the third day. The 
vascularization of the spinal ganglia is sufficiently provided for by 
the vessels accompanying the nerve stems and nerve roots. 
Voluntary impulses and inhibitions.— The nerve process 
originating in the gray matter of the central nervous system stands in 
a two-fold relation to muscular activity, — it either calls forth that 
activity or it puts a stop to it, it is either impulsive, motor, or it is 
inhibitory. What relation do these two varieties of the process bear 
to each other? Are they similar in nature? Are they similarly localized ? 
Is their difference due to different directions of their wave motion ? 
These questions and others have remained unanswered. Orschansky* 
thinks to throw light upon them by studying the time reactions of the two 
processes under various conditions. The masseter muscle was used, its 
great advantage being that, when the teeth are closed, the muscle can be 
made to contract and relax without the intervention of antagonistic mus- 
cles. Munk's idea that the impulse to relaxation of amuscle, /.<?., inhibition, 
^ArchivfurAnat. und Phys., Physiol. Abtheil., 1889, p. I73- 
