PHYSIOLOGY OF THE NERVOUS SYSTEM. 
non, but is chiefly due to a change in the 
circulation of the penis, to an increased attrac- 
tion of blood to the organ in virtue of the 
inflammatory state. 
Enough has been said to shew that, to lay it 
down that every act of ingestion, of retention, 
of expulsion, and of exclusion, is a reflex act, 
is opposed to all that we know of the intimate 
nature of these actions, The power resident, 
not in the spinal cord only, but in every ner- 
vous centre in which nerves are implanted, 
whereby, to use Prochaska’s words, sensory 
impressions may be converted into motor im- 
pulses, is no doubt of immense importance to 
the animal economy; but Dr. M. Hall has 
been evidently led, by an imperfect analysis of 
the functions we have been considering, to 
assign to this power too large an influence in 
them; and on the other hand, he has over- 
looked its obvious and important influence in 
other phenomena. 
Dr. Marshall Hall also attributes to the spinal 
cord a direct action or influence which mani- 
fests itself, first, in the tone, and secondly, in 
the irritability of the muscular system. 
I regret to be compelled to differ again from 
Dr, Hall with respect to this point, and to 
express my opinion that this dogma is incon- 
sistent with established doctrines of physiology. 
By the tone of the muscular system, I un- 
derstand that state of passive contraction which 
every healthy muscle exhibits when not in active 
contraction. It is this state which gives the firm, 
resisting, resilient feel, which the physician 
knows to be characteristic of a healthy state of 
the muscle. By virtue of it a muscle can 
adapt itself to changes which may take place 
in the distance between its two points of attach- 
ment; and it is in virtue of this property that 
a muscle shortens itself when the stretching 
force of its antagonist has been removed. 
When the muscles of one side of the face have 
been paralysed for some short time, the features 
lose their balance, because the muscles of the 
sound side have contracted to within a smaller 
space, having lost the resistance of those of the 
Opposite side. It is equality of tone which 
preserves the equilibrium between symmetrical 
muscles; it is tone or passive contraction 
which keeps hollow muscles quite closed, if 
they are empty, or firmly contracted on their 
contents, if not so, as the heart and intestine ; 
the tone of the predominant flexor muscles 
keeps limbs, whilst at perfect rest, in a semi- 
flexed position ; it is tone which keeps sphinc- 
ter muscles in a closed state. 
The question is, do the muscles derive their 
state of tone from the spinal cord, and is this 
property dependent on that organ ? 
This question is answered in the negative, if 
we can shew that there are good and sufficient 
grounds for affirming that muscles possess 
within themselves all the conditions necessary 
for the generation of their proper force. That 
muscles do enjoy these conditions is manifest 
from the following considerations: 1. their 
peculiar chemical composition, their main con- 
Stituent being fibrine, a substance which, we 
know from the phenomena of the coagulation 
721M 
of the blood, exhibits a remarkable tendency 
to contract; 2. their anatomical constitution ; 
the arrangement in fibres, the intimate texture 
of those fibres, which in the muscles of the 
greatest power, the voluntary muscles, is highly 
complicated; 3. from the large quantity of 
blood sent to muscles, which are probably more 
freely supplied with that fluid than any other 
texture in the body, and which receive it in the 
greater quantity when that contractile power is 
more active; 4. from the fact pointed out by 
Mr. Bowman, that a single muscular fibre, en- 
tirely deprived of all nerves, may be made to 
contract by a slight stimulus applied to any 
part of it; 5. from the knowledge which we 
now possess that the mechanism of these ac- 
tions may be seen by the microscope even in 
detached portions of muscular fibres ; 6. from 
the fact that muscles dissociated from the ner- 
vous centres by the section of all the nerves 
distributed to them, retain their power of con- 
traction for a very considerable period, long 
after the nerves which sink into them have lost 
their excitability. 
All these points afford the highest degree of 
probability that there is no direct dependence 
of muscle upon the nervous centres for the 
developement of its proper force ; and that this 
force is the result of the nutrient actions of 
muscle. The only way in which the nervous 
system can be said to have an influence upon 
the muscular force is by promoting the actions 
of the muscles, and thereby their nutrition. If 
a muscle have its nerves divided, and be left to 
itself, its nutrition fails after a certain period, 
and its contractility with it; but if it be exer- 
cised daily by galvanic stimulation, its nutri- 
tion remains unimpaired, and its contractility 
likewise. 
The tone of a muscle is nothing but the 
effect of the continuous developement of the 
muscular force resulting from the natural 
changes in the muscle; it is this state of ten- 
sion which denotes that these changes are 
actively proceeding, and that a uniform degree 
of attraction is being exerted between all the 
parts of the muscular fibre, in a degree propor- 
tionate to their masses, and that by this the 
muscles are maintained in a uniform state of 
‘tension so long as they are undisturbed by sti- 
muli conveyed to them through the nervous 
system, or from some other source. 
It seems, therefore, as reasonable as any pro- 
position in physiology, to affirm that the passive 
contraction or tone of muscles is due to a pro- 
perty inherent in the muscular tissue itself, and 
dependent solely on its proper nutrition, and 
that it is not derived from any other tissue. 
And if this be true, it is clear that the spinal 
cord cannot be the source of the tone of the 
muscular system. 
This statement is confirmed by the result of 
the experiment of removing the whole spinal 
cord in frogs or other animals. When this has 
been done, the limbs of the animal fall quite 
flaccid, the ‘muscles being no longer capable 
of preserving that degree of active contraction 
which is necessary to maintain attitude. A 
decapitated frog will continue in the sitting 
