70, 7§&&, 
ale at fetfelty to extlact in youl 
<Qoaca 
Action uf tlje 
LOUIS MACKALL, M. D. 
[Extract from an unpublished work.] 
69. The action of the Voluntary muscles is regulated by the 
law of nature that we have already stated, (37.) By virtue of 
this law, the determination of the nerve-fluid to a muscle is im- 
mediately followed by the active elongation of its fibres ; the 
contraction of a muscle or of its fibres as immediately follows 
the withdrawal of the nerve-fluid. In other words, the presence 
of the nerve-fluid, its cause of action, is, by virtue of this law, 
always attended by an active elongation of the fibres of a muscle ; 
while the absence of a due portion of this fluid is as constantly 
attended by the contraction of its fibres. 
By the aid of this law of nature, we have explained, I think, 
in a plain, intelligible, and rational manner, the phenomena pre- 
sented in the action of the involuntary muscles, that are placed 
about the walls of the tubes or hollow organs ; by the same aid, 
the phenomena presented in the action of the voluntary muscles 
may be as rationally and intelligibly explained. 
70. The minds of Physiologists of the present day are so fully 
impressed with the erroneous belief, so long inculcated in the 
books, that the active state of a muscle is that of contraction, 
and that the elongation of its fibres, (a state of which they pos- 
sess a very imperfect and false notion,) which they are pleased 
to call relaxation, is a passive state, that the converse of this 
proposition, as presented above, will be at first regarded by them 
with prejudice and aversion. The true law of nature in relation 
to this subject, however, when its application is attended to, in 
the extensive application of it we propose to present, must in 
time be acknowledged; if truth, as is said, has a tendency to 
prevail over error in the human mind. 2 
71. When we use the term muscle, it should be understood 
to embrace both the tendinous and fleshy portions of the organ ; 
the same fibres, we conceive, extend through the whole, and are 
influenced by the cause of action, the nerve-fluid, as well in the 
tendon as in the fleshy part. The latter portion differs from the 
former probably only in the circumstance of being more largely 
supplied with nerves and blood-vessels, by means of which, when 
the muscle is in a state of action, the special circulation of the 
nerve-fluid (43) is established. 
72. For the better illustration of their action, it will be found 
convenient to separate the voluntary muscles into the four fol- 
lowing classes, viz : 1st. Such as are attached by one extremity 
only, having the rest of the muscle free to be extended or re- 
tracted at will; 2d. Such as are attached at both extremities, 
but are capable only of the same motion as the former class, 
that of direct extension or retraction ; 3d. Such as are arranged 
circularly about the openings of the organs, and serve as sphinc- 
ters ; and 4th. Such as are attached to the bones at both ex- 
tremities, and act by making use of the bones as levers. 
THE ACTION OF THE FIRST CLASS OF VOLUNTARY MUSCLES, 
That are attached by one extremity, and have the rest of the muscle free to be 
extended or retracted. 
73. Of the action of this class we will advert to that of the 
muscles of the tentacles in the lower orders of animals ; and 
among the higher orders, to that of the muscles of the tongue, 
of the ciliary processes, and of the male Organ of generation. 
Perhaps there is no other instance in nature, in which is pre- 
sented so fairly and clearly, the true condition of a muscle when 
in a state of action, as in that of the action of the muscles of the 
organ last mentioned. Physiologists, by a resort to Sophistry, 
of which we shall speak again, have ignored the action of these 
muscles, which is the same with that of all other muscles; for 
the state of erection produced by the action of these muscles is 
common to all the muscles of the living body when in action. 
Every muscle when in action is in a state of vital erection; 
which term should be understood to express simply the active 
elongation of the fibres, with a due supply of blood and of nerve- 
fluid to maintain this state. In the Human subject, the true 
character of the organ of which we are speaking is masked, as 
it were, by the great development of the blood-vessels and nerves 
with which it is supplied; but this is not the case in some other 
species of animals, as in the Horse, the Ox, the Hog, and the 
Sheep. In these the main body of the organ is composed of lon- 
gitudinal muscular fibres that may be actively elongated to a 
length of from twelve to twenty inches. The view of muscular 3 
action heretofore presented may be repeated in connection with 
the instance before us. 
74. The suggestive impressions, appointed to precede the 
active state of this organ, having been duly received, the anima 
determines the nerve-fluid, in an extra supply, to its fibres through 
the sensory and motory nerves of this organ. In consequence, 
the proper longitudinal and other fibres of the organ become 
actively elongated, together with the fibres about the walls of the 
vessels and sinuses, in which there is an increased flow and 
accumulation of blood. With this accumulation of blood there 
is established the special circulation of the nerve-fluid to this 
point; the supply of this fluid is thus further enlarged, and the 
action of all the fibres is exalted to its extreme limit. This 
latter state of the organ is expressed by the term "Venereal 
orgasm." 
75. In this representation of the action of muscles, there are 
three points to which we desire to direct attention : the first is, 
the propriety of regarding the organ in question as a muscle 
attached at one extremity by two heads to the ossa pubis and 
ischia; the second is, the active elongation of the proper fibres 
of this muscle ; and the third is, the stiffening or rigidity of the 
same fibres when in action. The two latter points are particu- 
larly worthy of attention, as they occur in every instance of 
muscular action, and, what is very strange, have been entirely 
overlooked by physiologists. 
76. The Ciliary processes are the small muscles or bundles of 
muscular fibres that are attached by one extremity to the mar- 
gin or verge of the opening into the eye, called the pupil; and 
are so arranged that by their extension the pupil is diminished 
or the opening narrowed, and by their retraction the pupil is 
enlarged or the opening widened. Light is appointed to be the 
appropriate suggestive impression to precede the action of these 
muscles. When the eye, in its normal condition in the living 
body, is withdrawn from the light, the mind, not having received 
this suggestive impression, does not call into action these muscles, 
and they are consequently retracted, and the pupil is enlarged ; 
but when the eye is brought into the light and the impression is 
made, the mind determines the nerve-fluid to these muscles, and 
they become extended in proportion to the supply of this fluid ; 
by their combined action the pupil is diminished or narrowed, so 
as to exclude such quantity of light as might be injurious to the 
optic nerve. 
Here again we have a Vital erection, in the essential condi- 
tions-the active elongation, and apparently the stiffening of the 
fibres ; and it is worthy of remark here, that in inflammation of 
these and the adjoining parts, as in iritis, there is established 
the special circulation of the nerve-fluid to these fibres, and they 4 
become persistently elongated, and the pupil continues to be 
narrowed even when the eye is withdrawn from the light. 
77. The longitudinal muscular fibres of the Tongue (with a 
view to the elucidation of the action of this organ) may all be 
regarded as one muscle, that is attached at one extremity, with 
the other parts free to be extended or retracted at will. The 
active elongation or extension of these fibres when innervated, 
or when in action is manifest in our own persons, if we confine 
our attention to the fibres in question ; but this active elongation 
of the tongue in some of the lower orders of animals is very 
remarkable. Every one is familiar with the protrusion and 
elongation of the tongue of some of the domestic animals, as the 
Dog, the Cow, &c. 
This action of the tongue of the Serpent is deserving of par- 
ticular notice. When the animal is aroused or excited, it erects 
its head and thrusts out of its mouth its forked tongue, to the 
extent of several inches. The suddenness and celerity of the 
motion of the organ forcibly reminds us of the appearance of a 
flash of Lightning. 
It is impossible, I believe, to suggest any rational explanation 
of this phenomenon, other than that of the innervation and con- 
sequent elongation of the fibres of the muscles that belong to 
this organ. The suddenness and celerity of the motion precludes 
all other agency but that of the nerve-fluid, passing along the 
nerves; which alone resembles in its motion that of the Electric 
fluid. 
The action of the tongue of the Frog or toad, when it seizes its 
prey, is similar to that of the serpent. 
78. A notable action of this kind is presented in that of the 
tongue of the Chameleon. To facilitate its description, this 
organ may be divided into four parts ; first, the anterior bulbous 
portion, formed by the interweaving of cellular and muscular 
tissues-with the appearance of the end of the trunk of the 
elephant, it is furnished like this with a fleshy forceps at the 
extremity, with which the animal seizes its prey; second, the 
middle or interior portion, composed entirely of cellular tissue 
formed into a number of bands or hoops, having the intervals 
between them supplied with very loose and extensile meshes of 
this tissue; third, the lingual bone, being a process from the 
centre of the os hyoides, arranged in the direction of the tongue, 
on which, when the tongue is retracted, the cellular bands and 
meshes of the second portion, and a part of the bulbous portion, 
which is hollowed out for this purpose, are stretched or drawn, 
like the finger of a glove drawn over the finger; and fourth, two 
well-developed muscles, having their fibres arranged longitudi- 
nally, and largely supplied with nerves and blood-vessels. These 
muscles arise from the cornua of the Os hyoides, one from each, 5 
and being arranged one on each side of the tongue, or of the 
central cellular portion, are inserted in the bulbous extremity. 
When in a state of repose, or when retracted within the 
mouth, the organ is from an inch to an inch and a half long ; but 
when about to seize its prey, commonly an insect, the chameleon 
creeps to within seven or eight inches of the object, and then 
fixing its body, and taking aim, as it were, suddenly, and with 
the celerity of Lightning, thrusts forward its tongue, and seizes 
the insect with the fleshy forceps at its extremity. The food 
thus taken is then drawn into the mouth by the retraction of the 
organ. 
79. If what we have suggested be admitted to be the true law 
of muscular action-if innervation, or the determination of the 
nerve-fluid to a muscle, is attended with the active elongation 
of its fibres, there is no difficulty whatever in comprehending or 
in offering a rational explanation of the phenomenon before us. 
The animal, it will be understood, determines its nerve-fluid to 
the lingual muscles, and the tongue is extended to the distance 
mentioned, simply by the active elongation of these muscles. 
The food is also drawn into the mouth by the retraction of the 
same muscles, caused by the withdrawal from them of this fluid. 
But what explanation of this phenomenon can be given with- 
out the aid of this law ? We will give the only one we have met 
with worthy of any notice, that of Mr. John Hunter, in his own 
words, taken from the " Illustrated Catalogue of the Hunterian 
Museum." 
" This length of tongue, its extension and contraction, are very 
singular, and, if well understood, most probably very curious. 
" The cause and mode of the contraction of its length are not 
uncommon. The elongation of the tongue in this animal is per- 
haps like nothing that we are acquainted with in an animal body. 
" The apparatus for this purpose is a small rounded body 
which passes from the apex of the os linguae (glosso-hyal) to the 
bulbous part, and then through the centre of the bulb. The 
part between bone and bulb consists of two different substances, 
one a whitish substance, which is the firmest, and appears to be 
capable of keeping its form ; the other is softer and more trans- 
parent. That part which passes through the bulb consists only 
of one substance, and appears to be a sheath for the reception of 
the os linguae." The reader will please recollect that the ap- 
paratus, here described by Mr. Hunter, is nothing more than 
the bands and meshes of cellular tissue of which we have spoken 
above. But let him proceed : 
" The first of these («'. e. the whitish, firmer substance) appears 
to be composed of rings or something similar placed obliquely in 
contrary directions, so as to appear to be two spirals crossing 
one another. Whether the other or softer substance" [the cel- 6 
lular meshes. L. M.] " has any direction of fibres I could not 
observe, but I suspect it is muscular. If I am right in my con- 
jecture of this structure, and of its disposition, it will be no diffi- 
cult thing to show how it may be elongated; for if these rings 
are placed transverse, they may be brought so near to one ano- 
ther as to shorten the whole very considerably; and if they 
allow of being placed almost longitudinally, they must of course 
lengthen it very considerably, and this position can easily be 
produced by muscles, which I take the pulpy substance to be. 
" The contraction of the tongue is owing to a degree of elas- 
ticity ; but this appears to be only in the cellular membrane, 
acting as an assistant to the muscular. The muscular contrac- 
tion is owing to two muscles, one on each side of the tongue; 
each arises from the os hyoides on the inside of the os linguale, 
and passes along the side of the tongue to its bulbous part; but 
before it gets to the bulbous part it spreads itself all round. 
" In the centre of each of these two muscles passes a consid- 
erable nerve to the bulbous part, and also two arteries. When 
the two muscles act, they draw the tongue back upon the os lin- 
guale, which, as it were, passes through the middle elongator, 
then through the centre of the bulb, till the whole tongue is re- 
tracted. Although this middle body is drawn upon the os lin- 
guae, yet it does not appear to be a hollow like a pipe ; it rather 
appears to be filled with a very ductile cellular membrane, as in 
every part of the elongating division of the tongue, in order to 
allow of the great difference in the situation of parts with 
respect to one another." (Hunterian manuscript.) 
80. The Ant-eater (Myrmeco-phaga) furnishes a remarkable 
instance of the action of the muscles of this class. The tongue 
of this animal is composed of two distinct muscles having differ- 
ent origins, and a different disposition of fibres. To simplify the 
subject, we may say one of these muscles arises from the sternum, 
and passing along through the muscles on the anterior surface of 
the neck, terminates at the tip of the tongue-its fibres being all 
arranged longitudinally; the other muscle arises from the 
os hyoides, passes around the former longitudinal muscle in close 
spirals, forming a sort of case or sheath for it, and terminates 
with it, at the end of the tongue. 
When quiescent, or in a state of inaction, the tongue of the 
Ant-eater is probably about six or eight inches long; but when 
thrust into the ant-hills to secure its prey, Naturalists tell us, 
it is elongated or protruded to the extent of seventeen or eighteen 
inches.* 
The object attained by this curious arrangement of the mus- 
cles, in accordance with our view of muscular action, is evidently, 
* Curvier's Animal Kingdom, edited by Griffith, vol. iii, p. 300. 7 
the free and unimpeded extension of the longitudinal muscle to 
its full capacity, by preserving its fibres, nerves, and blood- 
vessels from external pressure, while threading the narrow 
passages of the ant-hill through which it is forced. This object 
is fully accomplished by the action of the spiral muscle, which 
tends to dilate these passages, or, at least, to enlarge and keep 
open the space enclosed by it, in which the longitudinal muscle 
acts. 
In the absence of this view, Physiologists have been forced to 
adopt the very absurd supposition, that the tongue of the Ant- 
eater is protruded by the contraction of its spiral muscle ! 
81. The Woodpecker, as is well known, feeds on the grubs 
that burrow into the limbs and bodies of trees. The burrows are 
first exposed by pecking through the bark with its strong, sharp 
bill, and then the long tongue, like a flexible probe, is thrust in, 
as the Ant-eater's into the ant-hill, and the grub being harpooned, 
as it were, is dragged forth. 
To adapt the organ to the purposes mentioned, the anterior 
portion of the tongue-I refer more particularly to that of the 
species called the Flicker, (Picus aureatus)-is composed of a 
horny, spear-shaped, barbed point; from this point there arise two 
muscles, tendinous at each extremity, but with fleshy bellies or 
middles-their fibres longitudinal; these muscles pass around 
the base of the cranium, one on each side, and then rest with 
free extremities in a groove or closed passage formed between 
the skin and cranium, and extending over the middle of the head 
from behind forward until it reaches the base of the upper Man- 
dible. Besides these, two other muscles arise, one from the 
ramus of the lower mandible on each side, and pass around the 
longitudinal muscles, forming a sheath for them through their 
whole length. The arrangement of these muscles are strikingly 
similar to that of the muscles of the tongue of the ant-eater, and 
doubtless their functions are the same. When the longitudinal 
muscles are innervated and elongated, the upper bill, which is 
then applied to the tree, becomes the basis or point of resistance, 
from which the tongue is projected into the burrows ; the other 
or spiral muscles acting, as suggested, when speaking of that 
of the ant-eater, to preserve the freedom of the motion of the 
former, by protecting from external pressure the blood-vessels and 
nerves with which they are largely supplied. 
The notion suggested by some, that the tongue is jerked for- 
ward by the contraction of the last-mentioned muscles, is absurd; 
as the means suggested are clearly inadequate to the end pro- 
posed. The contraction of any portion of these muscles could 
not effect a motion of the tongue to the extent of one inch, but, 
if contracted, the portions anterior to their origins would draw 
the tongue back, and counteract the effect of the contraction of 8 
the portions of these muscles that are posterior to their origins, 
so that no effect of the kind suggested, could result from the con- 
traction of these muscles. The tongue is thrust into the burrows, 
probably to a distance of from five to eight inches, judging from 
the extensibility of the organ in the living or recently killed 
bird. 
The longitudinal muscles of the tongue are commonly regarded 
as the cornua of the os hyoides, but I think it more rational to 
regard them as muscles (as their appearance clearly indicates) 
belonging to this class, attached at one extremity with the rest 
of the organ free, to be extended or retracted at will. 
82. The " Aij-Aij" is an animal whose habitat is confined to 
Madagascar. It presents several points in its natural history 
closely resembling those of the woodpecker. Like this, it feeds 
on a grub that burrows in the bodies of trees in that island ; and 
it exposes these burrows by tearing off the bark with its teeth. 
The animal then introduces a long flexible probe, and pulls out 
the grub. This probe, however, is not the tongue; but one of 
the fingers of one of the fore-paws, which is curiously adapted in 
its structure to this purpose. The anatomy of this organ is not 
generally known, but I presume, from the office it is said to per- 
form, that it is similar to that of the tongues of the Ant-eater 
and of the Woodpecker that we have just described. In its re- 
tracted state it may present the appearance of a " shrunken" or 
"atrophied" member, as is represented; but its muscles are, I 
doubt not, well developed, with large blood-vessels and nerves, 
and capable of an extensive action of elongation. 
83. The Tentacles of some of the lower orders of animals are 
so similar in structure, in their action, and in the purposes they 
subserve, to the tongues of the higher orders, that we are in- 
duced to regard them as their analogues. These organs are 
composed of muscles with longitudinal fibres, that are attached 
by one extremity around the outer margin of the mouth, and are 
extended or actively elongated for the purpose of collecting and 
of bringing into the mouth, the food or prey that may be floating 
in the element these animals inhabit. When the animals are 
reposing, or not feeding, these organs are retracted; but when 
engaged in taking their food, the tentacles are innervated, and 
actively elongated or extended. In some instances, as in the 
Physalus, the Enychoteuthis, &c., this extension is carried to a 
distance of six feet or more.* For a more minute account of the 
structure and office of these organs, I refer to the works on 
comparative Anatomy and Physiology. Our theory of muscular 
action offers to the intelligent student a number of suggestions 
that will be found of great use to him in his efforts to understand 
* General Structure of the Animal Kingdom, by T. Rymer Jones. 9 
the more complicated structure and action of some of these 
organs. 
THE ACTION OF THE SECOND CLASS OF VOLUNTARY MUSCLES, 
That are attached at both extremities; but their action is that of extension and 
retraction, simply. 
84. For the plainest instances of this action, we must again 
have recourse to some of the inferior orders of animals. The 
land Terrapin furnishes several instances of this character, in the 
protrusion of its head, in the opening of its valves, &c. 
From that part of the interior of the Carapax or top shell that 
corresponds to the lumbar vertebrae, arise two large muscles-one 
on each side of the vertebrae. Each of these muscles has three dis- 
tinct heads or bundles of longitudinal fibres, the longest of which 
arises from the most posterior vertebra, and extending along on the 
side of the dorsal and cervical vertebrae, is inserted into the Occi- 
put ; the other two bundles of fibres arise a little in advance of this, 
and are inserted into the two cervical vertebrae nearest the head. 
Any one, who understands this arrangement of the muscles, and 
who has become acquainted with our view of muscular action, 
will readily comprehend how the head of the Terrapin is protru- 
ded, simply by the innervation and consequent elongation of 
these muscles ; and he will as readily comprehend how the head, 
when protruded, can be retracted within the shell, by the with- 
drawal of the nerve-fluid from these muscles. 
85. In order to protrude the head, the Terrapin must first open 
its shells for this purpose. This it does by pushing down the 
anterior valve of the Plastrum or bottom shell, by which the 
space between the shells is closed. To enable it to do this, it is 
provided with two muscles, arising one on each side of the ante- 
rior dorsal vertebrae, which, passing down on either side of the 
neck, are inserted into the front edge of the anterior valve. By 
elongating these two muscles the valve is pushed down and the 
shells opened. The limbs of this animal are protruded and re- 
tracted by a similar arrangement of muscles, destined to this end. 
86. The Snail (Helix nemoralis) presents some remarkable in- 
stances of the action of muscles that belong to this class. The 
soft parts of this animal consist mostly in a large bundle or mass 
of longitudinal muscular fibres, with which the several parts, as 
the head, the foot, &c., are protruded from the helix or turbina- 
ted shell; that is, by the active extension of these fibres. 
The eyes of the Snail may be observed, when the animal is in 
motion, at the extremities of two fleshy tubes, or horns as they 
are commonly called, projecting from the head. From the mass 
of longitudinal fibres, two separate bundles or distinct muscles 
arise, and passing through the visceral cavity and traversing the 
horns, are inserted, one around the base of each eye, at the ex- 10 
tremities of these horns. When the Snail is at rest, the Ophthal- 
mic muscles are retracted, the horns inverted, and the eyes are 
thus securely packed away in the visceral cavity; but when it is 
aroused, and protrudes its head and foot, it also determines its 
nerve-fluid to the ophthalmic muscles, and by elongating them, 
pushes forth its eyes. The horns are tubes supplied with mus- 
cular fibres placed spirally about the walls ; and when the longi- 
tudinal muscles are extended these fibres are also extended; and 
in this way the calibres of the horns are enlarged, and thus allow 
a free action of the internal muscles with their nerves and blood- 
vessels. 
It will be observed that there is a striking resemblance in the 
arrangement and action of the muscles in this instance to those 
in the instance formerly mentioned of the tongue of the Ant-eater. 
The explanations given by Physiologists of these two phenomena 
are the same, and both are equally absurd. They say, the eye of 
the Snail is everted by the contraction of the spiral muscle of 
the horn! The longitudinal muscle, they suppose, is intended 
and used solely for the purpose of retracting the eye ! 
87. We will advert to but one other instance of the action of 
the muscles of this class ; it is to that of the muscles of the body 
of the Leech. • This animal is possessed of two fleshy discs, one at 
each extremity of the body, by means of which it attaches itself 
to the surface on which it crawls; the discs acting as cupping- 
glasses, and taking a firm hold wherever applied. 
The walls of the body of the Leech are mainly composed of 
muscular fibres, that are arranged in three distinct layers. The 
fibres of the outer layer are disposed circularly, those of the 
middle layer spirally; but the fibres of the internal layer are all 
arranged longitudinally. By means of the latter layer of fibres 
the progression of the leech is effected. When stationary, the 
discs are attached to a surface near each other; but when about 
to move forward, the leech first detaches the anterior disc, and 
then extending its body by elongating the longitudinal muscles, 
it again attaches this disc to the surface on which it is crawling, 
or to some near object. When this anterior disc is fixed, the 
posterior one is detached and brought up, by the retraction or 
contraction of the same muscles, to be attached again near the 
former. In this manner the leech moves from point to point in 
its progress, sometimes with considerable celerity. In the same 
manner, the progression of all crawling animals, Annelidans, 
Serpents, &c., is effected. They first fix some part of the body, 
and from this point the body is extended by the elongation of 
the longitudinal muscles, when they again fix the forward por- 
tion of the body, and by contracting these same muscles by with- 
drawing the nerve-fluid from them, they draw up their length 
from behind. 11 
But why do I say this of all crawling animals ? when the same 
mode of progression is common to all animals ; as will be ex- 
plained further on. 
ACTION OF THE THIRD CLASS OF VOLUNTARY MUSCLES. 
88. The shincters or sphincter muscles that belong to this 
class are composed of fibres arranged circularly around the open- 
ings about which they are placed, as the Orbiculares palpebrarum, 
the Orbicularis oris, &c. In a state of rest or of repose these 
muscles are moderately contracted, and the openings are closed: 
they may be more forcibly contracted and the openings more 
firmly closed by an intentional, persistent withdrawal of the nerve- 
fluid from their fibres. But when it is designed to bring into 
use the eyes or the mouth, the sphincter muscles are innervated, 
their fibres become actively elongated, and the openings are 
dilated or expanded. 
The error that has prevailed in relation to the action of these 
muscles has arisen from the difficulty in distinguishing the con- 
sciousness that attends the innervation of the muscles from that 
that attends the withdrawal of the nerve-fluid from them. The 
early physiologists mistook the one consciousness for the other ; 
and this mistake has continued in the books to the present time. 
They supposed that innervation was attended with the active 
contraction of the muscles and the closing or shutting of the 
openings. The really active state of the muscles they called 
relaxation, and supposed it was the result of inaction, or of an 
absence of the cause of action. 
89. The instances of the action of the voluntary muscles wre 
have already presented, are so plain, and the explanations given 
of the phenomena attending such action are so simple, intelligi- 
ble, and rational, that, it appears to me, they must produce in 
every well-ordered, unsophisticated''mind that considers them, a 
full conviction of the truth of the law of muscular action that we 
have suggested. 
The absurdity of former explanations of some of the above 
phenomena we have pointed out in passing; but there are, be- 
sides, explanations of others of these phenomena, given in accord- 
ance with the old theory, equally absurd and unphilosophical, to 
which we have not adverted. The explanations to which we 
allude are founded in sophistry, and are clearly traceable to this 
source. 
Finding it utterly impossible to furnish a rational explanation, 
with the received theory, of phenomena such as are presented in 
the protrusion of the tongue of the Serpent, above referred to, 
the Sophist, to get around this difficulty, invented a new term, by 
which all the facts of the case are obscured, covered up, and 
ignored. rrhe organs, the action of which he could not explain, 12 
were said to be composed of erectile tissue. He did not stop to 
demonstrate even to himself this particular tissue, which in reality 
has no existence, (for these organs, like all the other soft parts 
of the animal body, are possessed only of the cellular, the mus- 
cular, and the nervous tissues.) This was no part of his design, 
his sole object being accomplished by the invention of the term 
that would serve, as it has served, to deceive the unwary and un- 
reflecting. It is thought by these, to be a sufficient explanation 
of all such phenomena to say, that the organs concerned, are 
composed of erectile tissue, and become erected when actively 
elongated. 
The idea commonly attached to this state of these organs is, 
that they are injected with blood, and are in this way extended. 
The fallacy of this idea is easily shown, however, by calling to 
mind the facts, that these organs are elongated before receiving 
their extra supply of blood ; and that, in many of these instances, 
the celerity of the motion of the organ, as in the case before 
us, entirely precludes this idea. The blood could not, by any 
possibility, be transmitted through the vessels, with a velocity 
to correspond with the motion of the tongue of the serpent, as 
indicated above. 
ACTION OF THE FOURTH CLASS OF VOLUNTARY MUSCLES, 
That are attached at both extremities, but make use of the bones as levers. 
90. It is more difficult to convey a just conception of the 
action of this than that of any other class of voluntary muscles ; 
because the means employed to produce the results are, here, much 
more complicated. The bones of the limbs to which these mus- 
cles are attached, and which are made use of as levers, are pro- 
vided with two distinct sets of muscles, one on each of the two 
surfaces towards their line of motion ; and their motion is not 
produced by the action of either set of muscles exclusively, but 
is caused by forces exerted by both sets at the same time. I 
repeat, the movement of the limbs of animals is not due exclu- 
sively to the action of either of the two sets of muscles with 
which they are supplied, but each movement is effected by the 
action or active elongation of one set, and by the contraction of 
the opposing set. 
91. Before entering upon the explanation of the action of this 
class of muscles, it will be well to call to mind three important 
truths, that are essential to a clear understanding of this action. 
These are, First, that the action and the contraction of a muscle 
are both vital phenomena, to be met with only in the living body, 
and are not represented elsewhere in any part of the economy of 
nature. These states of the muscle in the living body are sui 
generis, and no proper idea or conception of them can be gained 
by comparing them to those of a cord or pulley of any kind or 13 
of any condition, whether as wet or dry, elastic or inelastic, &c. 
Second, that the contraction of a muscle is as much the result of 
the operation of a law of nature depending on the abstraction of 
the nerve fluid, as the active elongation of a muscle is the result 
of the law of nature depending on the presence of, or the deter- 
mination to it, of this fluid; and Third, that the operation of a 
law of nature is always attended with an exhibition of power, 
and consequently, the contraction of a muscle is attended with 
force or power, as well as its action or active elongation. 
Force, it must be admitted, is exerted in connection with the 
contraction of a muscle ; but it is all important that we should 
not associate in our minds the force, with this state of the muscle, 
and then call this state of contraction the state of action of the 
muscle. This is the grand mistake committed by Physiologists, 
that has led them to overlook entirely the true state of action of 
a muscle, together with the force that is also exerted in connec- 
tion writh this state ; and this mistake has led to their confusion 
of thought, and defective and erroneous views on the subject of 
muscular action. 
I must repeat, the active state, or the state of action of a 
muscle, is a state of active elongation of its fibres ; and in con- 
nection with this state, force or power is always exhibited. 
92. With the knowledge of the above truths, the explanations 
we proceed to give of the action of this class of muscles will be 
rendered intelligible. The instances we shall select for this pur- 
pose will be such as are plainest and most familiar; that is, those 
that are to be observed in the action of the muscles of the limbs, 
upper and lower, of the human subject. 
The action of these muscles are so misunderstood by physi- 
ologists, and so misrepresented in the books, that the technical 
terms employed to designate them are calculated to mislead. 
I shall, therefore, discard these terms as much as possible from 
our present consideration, and substitute others. In doing this, 
let it be understood, that those I propose are suggested only for 
a temporary use-to simplify the subject to the general reader, 
and to elucidate the principles involved. I hope, however, that 
some new terms for these muscles may be permanently adopted 
that will be more expressive of the true facts of the case than 
those now employed. 
93. The muscles on the anterior surface of the Humerus or 
bone of the upper arm, embracing the Biceps and Brachialis 
anticus, we shall regard as one muscle, and call it, from its posi- 
tion, the Prae-humeral muscle ; and that on the posterior surface 
of this bone, the triceps, we shall designate as the Post-humeral 
muscle. 
The Prae-humeral muscle, then, arises from the shoulder blade 
(scapula) near the joint of the shoulder, and from the bone of 14 
the upper arm, and passing along its anterior surface is inserted 
into the upper portion of the bones of the fore arm. 
The Post-humeral muscle arises also in part from the scapula, 
and in part from the humerus, and passing along the posterior 
surface of this bone is inserted into a process of one of the bones 
of the fore arm, called the Olecranon process, that projects behind 
the joint at the elbow. 
94. When the whole arm is extended or straightened out from 
the flexed position, the mode in which this extension is effected by 
means of the muscles just mentioned, after what has been said 
above, is plain and palpable. In this movement, the anterior or 
Prae-humeral muscle is actively elongated by the determination to 
it of the nerve-fluid ; and at the same time the posterior or 
Post-humeral muscle is contracted by having the nerve-fluid 
withdrawn. The motion, it will be observed, is produced by both 
muscles, the anterior and the posterior ; but the former only 
is in action, or is influenced by the cause of action-the nerve 
fluid-it is in a state of vital erection; while the latter is thrown 
into a peculiar condition, that of contraction, by the abstraction 
of the cause of action. Both of these conditions, that of active 
elongation and that of contraction, in the opposing muscles, are 
essential and indispensable in every movement of the limbs, and 
each of these conditions being the result, as we have seen, (87) of 
the operation of a law of nature, such movements are executed 
with a double force, or with two forces, one of which is derived 
from the operation of each of these laws of nature. 
The opposite movement of the arm-the flexing it at the elbow 
from the straight position-is produced by an opposite condition 
of the muscles engaged. In this movement, the posterior muscle 
is innervated and elongated, while the anterior muscle is con- 
tracted. This action of the posterior muscle is better shown, 
however, in the following instance : 
95. The action of the muscles by means of which the fingers 
are moved, will be best shown by regarding them as two muscles, 
one on each surface of the bones of the fore arm, from which 
they arise. We will call them for the present, the Prse-brachial 
and the Post-brachial muscle, each term embracing the long mus- 
cles that go to the several phalanges of the fingers on its re- 
spective surface. 
The anterior or Prae-brachial muscle arises from the bones of 
the fore arm towards the elbow, on the inner surface, and extend- 
ing along in front, passes with its long tendons across the palm 
of the hand, to be inserted into the several bones of the pha- 
langes of the fingers on their inner surface. 
The posterior or Post-brachial muscle in like manner arises 
from the upper portion of the same bones, but from their outer 
surface, and passing along on this surface, and with their tendons 15 
over the back of the hand, are inserted into the bones of the pha- 
langes of the fingers on their outer surface, extending along 
even to the extremities of these bones. 
96. The great difficulty in realizing the true action and agency 
of the muscles we have just spoken of, arises from the fact men- 
tioned above, when speaking of the sphincters ; namely, that few 
minds are capable of distinguishing the consciousness or the 
mental sensation that attends the determination of the nerve- 
fluid to a muscle, that causes its action, from the consciousness or 
sensation that attends the abstraction of this fluid, that causes 
the contraction of a muscle. To make this distinction, it requires 
a patient education and training of the mind, more especially in 
those who have given some attention to physiology, and who have 
their minds pre-occupied with erroneous views of muscular action. 
This mental preparation, however, is what few or none have set 
about; but when this difficult task is accomplished, it will be 
observed, that, 
97. In flexing the hand, as in forcibly shutting it, or in grasp- 
ing any object firmly, a determination of the nerve-fluid is made 
to the posterior or Post-brachial muscle; and its fibres becoming 
actively or forcibly elongated, tend to produce the movement 
indicated ; at the same time, the nerve-fluid is withdrawn from 
the anterior or Prse-brachial muscle, and its fibres becoming for- 
cibly contracted, the act of shutting the hand, or of grasping, is 
perfected and completed. 
The opposite states of these muscles-that is, the innervation 
and extension of the anterior, and the enervation and contraction 
of the posterior muscle-it is evident, would produce the contrary 
movement of the fingers, the extending or straightening themout. 
98. If I have succeeded in explaining to the satisfaction of the 
reader, the action and agency of the muscles engaged in effecting 
the movements of the upper extremities, there will be no diffi- 
culty whatever in his comprehending the action and agency of 
the other muscles of this class that are concerned in the various 
voluntary movements of the living body. In all such movements, 
we repeat, two sets of muscles are concerned, whose action is 
opposed, the one to the other ; but the position established is the 
result of the agency, mainly of the set that is in a state of action, 
although in some measure attributable to the contraction of the 
opposing set. Thus, in assuming and maintaining the erect posi- 
tion of the body, the muscles, on the anterior surfaces of the 
lower extremities, of the spinal columns, and of the walls of the 
abdomen and thorax, are brought into action, and the result is 
accomplished, principally by the agency of these muscles, but in 
some measure also, by the contraction of those on the opposite 
surfaces. Again: 
99. In locomotion, of the biped, for example, it is true, the 
hinder foot is brought up to the advanced position ; and, again, 16 
the foot is raised to be carried forward by the contraction of one 
set of muscles ; but the progressive motion-the extending the 
leg and foot in advance, and the projecting forward of the whole 
body-is effected by the action, the active elongation, or exten- 
sion of the other set; or the opposite conditions of the same mus- 
cles may be employed for both of these purposes. 
The mode of progression, we have said, (87) is the same in all 
animals. In all, a portion of the body is advanced from a fixed 
point by the action or extension of certain muscles, and in all, a 
portion of the body that is behind this point is brought up by 
the contraction of certain muscles. In this respect the halting 
gait of the biped-that is to say, when, in walking, he keeps the 
same foot always in advance, bringing up the hinder foot to it, 
and then moving the front foot forward again-is the same with 
the natural gait of the snail; and, again, the snail would imitate 
the natural gait, or the continued progressive motion of the 
biped, if, instead of attaching its hinder disc in the rear of the 
front one, it could carry it along forward, and attach it in an ad- 
vanced position, and so continue its motion, carrying its discs 
alternately forward. 
100. The arrangement of the muscles, however, in the lower ex- 
tremities is somewhat different f-om that of the upper. The exten- 
sion of the leg on the thigh is effected by the action of the muscles 
on the posterior surface of the thigh bone or femur, while the leg is 
flexed on the thigh by the action of the muscles on the anterior sur- 
face of this bone ; and, again, the action of the tibialis anticus, 
and of the anterior longus digitorum on the anterior surface of the 
leg or tibia, tends to extend or straighten out the foot on the 
leg; and of the latter, to flex the toes on the sole of the foot; 
while the action of the muscles on the posterior surface, the Gas- 
trocnemius, the Soleus, and the posterior longus digitorum, &c., 
tends to flex the foot upon the leg anteriorly at the ankle-that 
of the two former by pressing the os calcis as a lever, and 
of the latter by extending and directly raising the toes. 
A curious circumstance, confirmatory of the correctness of this 
view of the action of the muscles of this region, is mentioned by 
Mr. John Hunter, who suflere 1 from a fracture of the tendon of 
the gastrocnemius, called the tendo Achillis. When this fracture 
occurred, he experienced, he says, the greatest difficulty in raising 
the toes from the floor, in walking across the room. 
Nothing has been said of the contraction of the opposing sets of 
muscles which assists materially in the movements just mentioned, 
because that will, of course, be inferred from what had been said 
above ; and to avoid encumbering the subject, relating to the 
physiological principle here advocated, we have omitted altogether 
the consideration of the mechanical principles of the Lever and 
Pulley that are involved in all the movements of the extremities.