PHYSIOLOGY OF THE NERVOUS SYSTEM. 
their production. And anatomists explored 
the frequent and often intricate anastomoses 
of nerves in their peripheral distribution with 
the hope of finding in them some clue to the 
explanation of these phenomena. 
To these actions I prefer to apply the name 
physical nervous actions to mark their peculiar 
characteristic, namely, independence of the 
mind, and to denote that they are the result of 
a physical change produced by a physical im- 
pression, and therefore, in their causation, wholly 
independent of mental influence. The term ex- 
cito-motory has been applied to them by Dr. 
Hall. To this term, however, there appear to 
me to be several serious objections. First, this 
term implies that the excitation of motion takes 
place in no other way than by a mechanism 
similar to that by which these movements are 
produced. Secondly, it denotes the existence of 
a peculiar excito-motory power different from 
the ordinary vis nervosa, the agent in all ner- 
vous phenomena. As if this force were not 
capable of being roused into action at one time 
by a mental stimulus, at another by a physical 
stimulus, or at a third by a mental and phy- 
Sical stimulus united. Persons get into the 
habit of using the terms “excito-motory power,” 
* excito-motory phenomena,” as if this power, 
or these phenomena were something quite pe- 
culiar, quite sw: generis, and limited to a spe- 
cial part of the nervous system, losing sight of 
the real truth that they differ from voluntary 
actions only in their mode of excitation, that 
is, by a physical and not by a mental stimulus. 
Thirdly, it limits the reflecting power of the 
nervous centres (i.e. the propagation of the 
change induced by the application of a physical 
stimulus at the periphery) to reflection from 
Sensitive to motor nerves. Now there are many 
facts which shew that reflection may take place 
from a sensitive to another sensitive nerve, and 
many of the phenomena of sympathy admit of 
no other explanation excepting on this prin- 
ciple. And I am by no means prepared to 
affirm that reflection may not take place from 
motor to sensitive nerves, or even from motor 
to other motor nerves, under circumstances of 
an exalted polarity of the nerves and the centres. 
Fourthly, some of these so-called excito-motory 
phenomena have nothing to do with muscular 
action. Take, for example, erection of the penis: 
it has not been shown that muscular fibres take 
any part in the production of this phenomenon, 
or that the stimulus which gives rise to it does 
more than create a change in the vessels of the 
penis, which seems due to muscular relaxation 
rather than to muscular contraction. The exci- 
tation of a gland to secrete by stimulating some 
surface connected with it, as the mammary 
gland by stimulating the nipple, is no doubt 
a phenomenon of the same kind, but not one 
in which muscular fibres are excited to contract. 
The term “ reflex actions,” in accordance 
with Prochaska’s view of the reflecting power 
of the nervous centre, is objectionable inas- 
much as it fails to denote fully the physical 
character of the phenomena ; and, moreover, it 
1s applicable only to a class of the actions in 
question, those, namely, in which the excitation 
VOL, IIT. 
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of a motor or sensitive nerve takes place through 
the primary excitation of another motor or sensi- 
tive nerve. Either this term, however, or that 
which I have proposed, may be used without in- 
convenience to science because they involve no 
particular theory, and yet sufficiently express 
some leading feature of the phenomena, 7eflec- 
tion at the centre, in the one case—a physical 
exciting cause of a phenomenon purely physical 
in the other. It may be objected to the term 
“physical nervous action” that the actions 
produced by the mental stimulus are equally 
physical in their intrinsic nature. When, how- 
ever, the term is habitually used in contrast with 
“ mental nervous action,” all practical difficulty 
or objection vanishes—both are physical pheno- 
mena,—but one is physical in its essence and 
also in its exciting cause; the other is physical 
in its essence, but mental in its cause. The 
term physical nervous actions may be regarded 
as a generic expression for all those nervous 
phenomena in which the mind takes no neces- 
sary share; reflex actions being a specific term 
denoting those physical nervous actions of which 
reflexion at the centre is a prominent character. 
In this sense I shall use these terms respectively. 
By none were these phenomena more care- 
fully studied than by Whytt and Prochaska. 
In 1764 Whytt published his “ Observations 
on Nervous Diseases,” a work full of the most 
valuable clinical and practical information. In 
the first chapter of this book, “ on the structure, 
use, and sympathy of the nerves,” he enumerates 
Various instances of sympathetic actions, and 
discusses the mode of their production. To 
show that he regarded in this light the actions 
which we are now considering, I shall quote 
one which he adduces as an example. He 
says: “ When the hinder toes of a frog are 
wounded, immediately after cutting off its 
head, there is either no motion at all excited 
in the muscles of the legs, or a very inconsider- 
able one. But if the toes of this animal be 
pinched, or wounded with a penknife, ten or 
fifteen minutes after decollation, the muscles 
not only of the legs and thighs but also of the 
trunk of the body are, for the most part, 
strongly convulsed, and the frog sometimes 
moves from one place to another.’’* 
Whytt’s most important work, in which this 
subject has been most fully discussed, is the 
essay on the vital and other involuntary motions 
of animals, published ten years earlier, in 1754. 
This physiologist was deeply imbued with a 
righteous dread of materialism, which led him to 
such extraordinary lengths in spiritualism, that 
he ascribed every action and movement of the 
body to “ the immediate energy of the mind 
or sentient principle;” while he completely 
repudiated all notion of any mechanical dispo- 
sition in the intimate nature of these pheno- 
mena. Asan example of his mode of reason- 
ing upon this subject, and as further evidence 
that he was well acquainted with the class of 
actions which we now call reflex or physical, 
the following passage from the eleventh sec- 
tion of this essay may be cited :— 
* Whytt’s Works, 4to. edit. p. 501. 
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