ON THE ACTIONS OF MUSCLES PASSING OVER MORE THAN ONE JOINT, by JOHN CLELAND, M.D., Professor of Anatomy and Physiology, Galway. THE muscles of the limbs are easily grouped into those which pass over one joint each, and those which pass over more joints than one; which latter may for brevity be called long muscles. The long muscles are functionally divisible into three sets, not quite distinct one from another. Some habitually produce mQvement in one continuous direction in all the joints over which they pass, as for example the flexors and extensors of the fingers, the short flexor of the toes, and the pectoralis major; others cause simultaneous move- ment in opposite directions to take place at different joints which they influence; and to this group the sartorius, the lumbricales, and the dorsal interossei belong': while a third set may be distinguished as consisting of muscles which, although calculated to cause motion in one direction at the different joints over which they pass, are yet in the ordinary gestures of the body so combined in action with other muscles that when at one of those joints there is movement in one direction, at the other there is movement in the opposite. It is to this last set of muscles, including the biceps and long head of the triceps of the arm, the gastrocnemius, the hamstring muscles, &c., that the following remarks refer. The peculiarities of these muscles first attracted my attention, while making dissections of the horse, nearly four years ago; and I briefly brought them under the notice of the physiological section of the British Association at Newcastle. The coraco-radialis muscle of the horse, corresponding with the biceps of the human arm, is a tough and compact muscle nearly in- cased in a tendinous sheath, and divided by numerous tendinous septa arranged longitudinally within it. To these are attached its short oblique muscular fibres, arranged in compound pennate fashion and ex- tremely numerous, but varying in length from so short an extent as a quarter of an inch to not much more than half an inch: and in the centre of the muscle is imbedded a strong ligament which passes uninterruptedly from the scapular to the radial attachment. From near the lower end of this ligament a tendinous slip, corresponding with the semilunar fascia of the human subject, passes downwards in 1 The peculiar action of the lumbricales and dorsal interossei muscles in at once flexing the proximal phalanges and extending the others, mentioned by Hunter (Collected Works, Vol. iv. p. 237), is very frequently overlooked. My attention was drawn to it by Professor Goodsir.
Transcript
ON THE ACTIONS OF MUSCLES PASSING OVER MORETHAN ONE JOINT, by JOHN CLELAND, M.D., Professor ofAnatomy and Physiology, Galway.
THE muscles of the limbs are easily grouped into those which passover one joint each, and those which pass over more joints than one;which latter may for brevity be called long muscles. The longmuscles are functionally divisible into three sets, not quite distinctone from another. Some habitually produce mQvement in onecontinuous direction in all the joints over which they pass, as forexample the flexors and extensors of the fingers, the short flexor ofthe toes, and the pectoralis major; others cause simultaneous move-ment in opposite directions to take place at different joints whichthey influence; and to this group the sartorius, the lumbricales, andthe dorsal interossei belong': while a third set may be distinguishedas consisting of muscles which, although calculated to cause motionin one direction at the different joints over which they pass, are yetin the ordinary gestures of the body so combined in action with othermuscles that when at one of those joints there is movement in onedirection, at the other there is movement in the opposite. It is tothis last set of muscles, including the biceps and long head of thetriceps of the arm, the gastrocnemius, the hamstring muscles, &c.,that the following remarks refer.
The peculiarities of these muscles first attracted my attention,while making dissections of the horse, nearly four years ago; and Ibriefly brought them under the notice of the physiological section ofthe British Association at Newcastle.
The coraco-radialis muscle of the horse, corresponding with thebiceps of the human arm, is a tough and compact muscle nearly in-cased in a tendinous sheath, and divided by numerous tendinous septaarranged longitudinally within it. To these are attached its shortoblique muscular fibres, arranged in compound pennate fashion and ex-tremely numerous, but varying in length from so short an extent as aquarter of an inch to not much more than half an inch: and in thecentre of the muscle is imbedded a strong ligament which passesuninterruptedly from the scapular to the radial attachment. Fromnear the lower end of this ligament a tendinous slip, correspondingwith the semilunar fascia of the human subject, passes downwards in
1 The peculiar action of the lumbricales and dorsal interossei muscles in at onceflexing the proximal phalanges and extending the others, mentioned by Hunter (CollectedWorks, Vol. iv. p. 237), is very frequently overlooked. My attention was drawn to it byProfessor Goodsir.
86 PROFESSOR CLELAND, ON THE ACTIONS OF MUSCLES
front of the radius to the great extensor of the metacarpus, and,continuing on the surface of that muscle, goes on to join its inferiortendon. There is thus completed an uninterrupted fibrous connectionbetween the scapula and the cannon bone; and although the lowerof the two bands which form it is nothing more than a strongaponeurosis, yet its existence is sufficient to show that those limitsto movement which it determines in the dissected limb existed inlife. By means of the brachial ligament described, flexion of theshoulder causes a corresponding amount of flexion of the elbow; andextension of the elbow causes extension of the shoulder: also theupper extremity*of the tendon to the cannon bone being pulledupward in each extension of the elbow, the carpus is pulled into theextended position at the same time.
The whole arrangement belongs to a mechanism by which theweight of the body is supported on the straight limb without the aidof muscular contraction. Thus when the shoulder and elbow-jointsare being extended in setting the limb to the ground, the band tothe cannon bone ensures the simultaneous extension of the horse'sknee: once on the ground, that joint and the joints below are keptextended by their construction and the pressure from above; but theflexors of the carpus are so short as to admit of very little flexion ofthe elbow when the knee is extended; they therefore support thehumerus when its upper extremity is pressed on from above; andthis they do, not by active contraction, but in virtue of their shortness;the coraco-brachialis and its contained ligament, maintain withoutmuscular contraction, the proper amount of extension of the shoulderas long as the elbow is extended; and lastly, the weight of the thoraxis suspended between the scapuloe principally by means of theserrati magni muscles, without these muscles being necessarilyactively contracted.
In the hind limb of the horse arrangements of the same descrip-tion exist. Thus the flexor pedis perforatus, which is attachedsuperiorly above the condyles of the femur, has its muscular fibresstill shorter and more separated by tendons than the coraco-radialis;the length of fibre being about a quarter of an inch, and the arrange-ment such that the total shortening of the whole muscle cannotexceed that of a single fibre; and in front of the leg a ligament inconnection with the flexor metatarsi binds the femur and metatarsusso closely together that flexion of the stifle joint compels flexion ofthe hock to a corresponding extent. In fact, the advantages ofconstruction which the horse's limbs exhibit for the production of theseries of movements required by the animal's habits, are obtained bymeans which involve a narrow limit to the variety of movements;some of the muscles being associated with ligaments, and restricting
PASSING OVER MORE THAN ONE JOINT.
motion as much as mere ligamentous bands would, while others moreor less approach the same disposition.
But the limit of motion by the shortness of muscles is not anarrangement confined to one animal, although perhaps in the horsethe principle is carried to a greater extent than in any other. Theelbow of the cat can be bent by moving the shoulder-blade. In birds,extension of the elbow compels extension of the metacarpus; theextensor carpi radialis being too short to admit of the metacarpusremaining flexed when the elbow is extended, and the humeralattachment of the muscle thus drawn further from the radius. Also,in perching birds, the flexion of the metatarsus on the leg, caused bythe weight of the body, is sufficient to produce flexion of thephalanges, so that the bird grasps its perch with little muscularexertion.
Instances of the same description of interdependence of joints areobservable in the buman body. Few persons, if any, can combinecomplete flexion of the hip with extension of the knee, the hamstringmuscles being too short to admit of it; and therefore flexion of thehip-joint ought to be avoided by the surgeon, where maintained exten-sion of the knee-joint is desirable. When the knee is bent the foot canbe flexed on the leg to an extent which, when the knee is extended,the gastrocnemius prevents; and in a limb severed from the trunk thestraight knee can be bent by pushing up the front of the foot. If thewrist be overextended, and it be then sought to straighten thefingers, it will be found that movement forwards at the wrist will takeplace in the attempt. It is to be observed, however, that although inthese various instances certain combinations of attitude in neigh-bouring joints are prevented, it is seldom, if ever, that in the naturalmovements of the body this property of muscles is brought into play.It is only by putting the limbs in positions uncomfortable, unusualand useless, that the shortness of the muscles is discovered. Thus,for example, the shortness of the hamstring muscles is illustrated bythe difficulty of accomplishing one of the feats demanded of men ondrill, namely, to touch their toes with their fingers, while the kneesare kept straight; but this position is one which would never beassumed for any practical purpose, and although it may be ingeniouslyfitted for the torture of apoplectic soldiers, it is not likely to give free-dom of movement in the proper use of the joints; being only calculatedto stretch the hamstring muscles to a greater length than usual,which has not been shown to be any advantage.
The combinations of movement most frequently observed in thehuman limbs are of precisely the same nature as those which are theonly movements allowed-in the limbs of the horse. Thus in the usualgestures of the arms, whether in grasping or rejecting, the shoulder
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88 PROFESSOR CLELAND, ON THE ACTIONS OF MUSCLES
and the elbow are flexed simultaneously, and simultaneously extended;and even in suddenly throwing the arms forwards when they arehanging at rest by the side, the natural movement is not to swingthem forwards at once from the shoulder, but to flex the shoulder andelbow-joints, then dart both arm and forearm forwards together, inthe same way as in rowing. Thus also with regard to the lowerlimbs in running, as well as in rising and sinking on the straighteningand bending legs, the hip, the knee and the ankle are extended andflexed together; and this is also the case in walking, except in thatpart of the process in which the limb is thrown forwards in front ofthe body. But in straightening the elbow and throwing forward theshoulder together, the biceps muscle is pulled upon at the elbow,while the arm at the shoulder moves as if yielding before thatmuscle; and the straightening of the elbow approximates the attach-ments of the triceps muscle, while the simultaneous extension of theshoulder increases the distance over which the long head of thetriceps is stretched at its upper end. Similarly to this, in themovements of walking, the hamstring muscles, the rectus femoris,and the gastrocnemius are not alternately stretched and contracted;but as each has its distance over one joint shortened, it has the dis-tance over which it passes at the other joint increased.
What then is the action of all these muscles in movements of thesort described? In the foreleg of the horse the whole shortening ofthe coraco-radialis, supposing that muscle to contract either in aid ofextension of the shoulder or flexion of the elbow, is certainly lessthan half an inch; and a shortening of half an inch will producescarcely any movement in the limb of so large an animal as a horse.In like manner, the flexor perforatus of the hind-limb can producehardly any effect by mere change of length, seeing that the extentof its possible contraction is less than a quarter of an inch. Butwhile it is obvious that these short-fibred muscles are not the activeelements which produce extensive movements in the joints overwhich they are placed, a little reflection will make it clear, thatwhatever the length of fibre of the muscle whose action we consider,if the movements of the limb resemble those of the horse in being ofsuch a description that the attachments of the muscle, instead ofapproaching and separating, remain at a pretty uniform distancethroughout, that muscle cannot be the moving agent. And this is acase which actually occurs. Thus I have mnade measurements of thedistance from the superior to the inferior attachment of the gastro-cnemius muscle, when both knee and ankle were completely flexed,and when they were both completely extended, and have found thatthe distance remains unchanged. If we sink upon the bended knees,flexing the limbs completely and remaining balanced on the toes,
PASSING OVER MORE THAN ONE JOINT.
then rise to our full height on tip-toe, the length of the gastrocnemiusremains unchanged in the movement. Therefore the belief that thismuscle acts similarly to the soleus, and in conjunction with it, isaltogether erroneous; and it may be truly said, that had no othermovements been required than those involving uniform relation ofankle and knee, a ligament would have served the purpose of thegastrocnemius miuscle.
Let us suppose the semimembranosus muscle, the rectus femorisand the gastrocnemius to be each replaced by a ligament, and let thesemitendinosus and biceps be left, for simplicity's sake, out of conside-ration. In bending the limb, the hip-joint being flexed by the ilio-psoas, the knee would be compelled to bend by the semimembranosuspreventing the upper end of the tibia increasing its distance from theischium, and, in the case of the limb being free, the ilio-psoas wouldhave thrown upon it the muscular effort required to bend the knee aswell as the hip. On the other hand, if the limb were benit beneaththe weight of the body, the gastrocnemius, being pulled down by theflexion of the ankle, would drag down the thigh, and the rectusfemoris stretched over the bent knee would pull forwards the pelvis,and so flex the trunk on the femur; and thus flexion of theankle would compel flexion of the hip-joint. In straightening thelimb, the soleus, the vasti and crureus, and the gluteus maximuswould continue to extend the ankle, knee and hip respectively; butwhile the action of the soleus would be confined to the ankle-joint,because in the human subject, contrary to what is the case in quad-rupeds, no muscle of the dorsum of the foot extends over the knee tothe femur, the action of the other muscles enumerated would not beconfined to the joints over which they pass. For the extension of thethigh from the hip, by the gluteus maximus would drag the kneestraight by pulling upwards the rectus femoris, and the straighteningof the knee would extend the foot by dragging upwards the gastro-cnemius. So also contraction of the vasti and crureus would act onboth ankle and hip-joint by dragging up the gastrocnemius andpulling down the semimembranosus. Now it is easy to perceive thateffects such as we have been supposing to be produced by ligamentsare actually produced habitually by muscles. This is obviously thecase wherever the points of attachment of a muscle remain withoutalteration of distance throughout a movement of the limb; it isobvious also when the points of attachment become further removedone from the other during the movement; and even where there isshortening of the muscle, there is a mixture of the same ligamentousaction whenever the more fixed attachment is dragged in a directionaway from the point occupied, at the commencement of the move-ment, by the more mobile attachment.
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I think that I have now made it very plain that the action of thehamstling, rectus femoris, and gastrocnemius muscles in the lowerlimb, and of the biceps and long head of the triceps in the arm, is inthe ordinary series of movements chiefly of a ligamentous character,and that action of the same description enters as an element com-bined with true muscular action in the accomplishment of movementsby other muscles.
One effect of ligamentous action of long muscles is to give to shortmuscles an indirect action on joints over which they do not pass. Thusif the rectus femoris remain tonically of such length that whenstretched over the extended hip it compels extension of the knee,then the gluteus maximus becomes not only an extensor of the hipbut an extensor of the knee as well. Such indirect action may eithercome into operation to make muscles which attach limbs to the bodyefficient in moving distant joints in the neighbourhood of which itwould be inconvenient to have large masses of muscle, or may causethe action of two groups of powerful short muscles to be effective onone or other joint as may be required. The first of these advantagesis illustrated in the limbs of horses, and still better in the wings ofbirds, in which the powerful pectorales muscles and their antagonists,largely developed and lying against the body, are made the motoragents of all the joints of the wing, which are thus left comparativelyunincumbered with the weight and bulk of muscle. The otherprinciple is illustrated in the lower limbs of man, for if the gluteusmaximus act on the knee-joint through the rectus, and the vasti andcrureus on the hip-joint through the hamstring muscles, then thetotal amount of muscular power is made available for overcoming thetotal amount of resistance, whichever be the joint on which that mayto the greatest extent fall.
The action of muscles thus ligamentously employed differs, how-ever, in various respects from that of mere ligament. Taxed beyondits strength a ligament will be ruptured, whereas a contracted muscleis easily relaxed: also, if neighbouring joints be united by ligaments,the amount of flexion or extension of each must remain in constantproportion to that of the other; while, if the union be by muscles, theseparation of the points of attachment of those muscles may varyconsiderably in different varieties of movement, the muscles adaptingthemselves tonically to the length required. In these circumstancessufficient reason is to be found for the employment of an organicaction involving waste of tissue and energy, instead of bands withmere mechanical strength; and it is also to be recollected that atruly motor action is often combined with the ligamentous, and thatoccasionally the muscles, whose ligamentous function is most marked,are called on to act in a wholly different manner from that in which
PASSING OVER MORE THAN ONE JOINT.
they usually do, passing at once from greatest contraction to greateststretch. For example, a movement of this description occurs in thearm in the wielding of a sabre or sledge-hammer; for if the elbowbe flexed and the hand thrown behind the head, both elbow andshoulder are placed so as to approximate the attachments of thebiceps; and when the arm is then thrown forwards, the shoulderbrought down, and the elbow extended, the biceps is stretched overboth joints, while the long head of the triceps has its attachmentssuddenly approximated. So also, in the lower limb, in the move-ment of kicking, the hamstring muscles have their attachments atfirst approximated by overextension of the hip and flexion of theknee, then when the limb is swung forwards they are placed onfull stretch, and the rectus femoris has its attachments approximated.Both of the movements mentioned, however, differ from those of theordinary series, in being of a sudden and not of a sustained character,and in having the action, which is commenced by a violent muscularcontraction, continued by the impetus of the swing of the limb; andin neither movement can the long muscle, whose attachments areapproximated, be considered as at all the principal muscle which iscalled into play.
Besides diffusing to distant joints the action of short muscles, asecond advantage is gained by the long muscles in those instancesin which the ligamentous function is combined with contraction,namely, that the contractile force is greater than it would otherwisebe. For a less amount of shortening takes place than would benecessary to produce the desired effect on the joint which yields tothe muscle, if the far extremity of the muscle were not draggedaway from that joint; and it is allowed that the force of contractionof a muscle diminishes as the muscle shortens; that the force withwhich a muscle may be maintained in full contraction is less thanthat with which it is capable of maintaining the semi-contractedcondition.
As a corollary to the proposition that the action of long musclesin those movements in which their length is unchanged is ligament-ous, it may be laid down that in these circumstances they addnothing to the velocity of the movement, for they only convey fromone joint to another the effects of the contraction of other muscles.Thus the rapidity with which the forearm is thrown forwards andwithdrawn in the movements of boxing is quite unaided by thebiceps and long head of the triceps, and produced altogether by themuscles which act on the shoulder and elbow-joints separately. Infact, the long muscles when acting ligamentously are diffusers andcombiners, but are not producers of movement.
Various of the statements now made as to the mode of action of
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92 PROFESSOR CLELAND, ON THE ACTIONS OF MUSCLES
long muscles find illustration in the following measurements of thehamstring muscles made on a dissected limb.
Greatestpossiblesepara- Length in Length in Nearesttion of Greatest extension flexion of approxi- Length ofattach- stretch. of hip and hip and mation of fibre.ments ke. ke.attach-after divi-ke. ne ments.
From this table it appears that none of the hamstring muscles arelong enough to permit the combination of complete flexion of thehip-joint with complete extension of the knee.
It must be explained that in each muscle the different fibres werefound to be of the same length, and that the measurement of fibre, inthe case of the semitendinosus, has reference to the length of a fibreabove or below the tendinous intersection, added to the length ofthat which was continuous with it on the other side of the inter-section; and it must be borne in mind that in all three muscles thearrangement of the fibres is such that the contraction of one fibrerepresents the total possible contraction of the muscle. It will nowbe seen that the greatest approximation of attachments in the dis-sected limb was in each case a position incapable of being reached bythe contraction of the muscular fibres, for the difference betweengreatest stretch and greatest approximation of attachments was inthe semitendinosus 63 th inches, which to be obtained by contractionwould require each fibre to be shortened to 1 th inches; while in thesemimembranosus and biceps the differences between greatest stretchand greatest approximation of attachments were in the two musclesrespectively 31 and 33- inches, lengths greater than the length offibre in each case. But the rectus femoris had been removed, andthat muscle limits the approximation of attachments of the hamstringmuscles, as may be shown by throwing back the thigh and pressingthe raised foot towards it with the hand, when pain will be felt inthe rectus femoris, and the movement will be checked by it beforereaching the amount of flexion of the knee which is possible whenthe hip is flexed.
It will be noticed that the semitendinosus contrasts very decidedlywith the biceps and semimembranosus, in respect that while the short
PASSING OVER MORE THAN ONE JOINT. /l.- i
fibres of these muscles undergo only a very slight contracto fiiitipassage from extension to flexion of the limb, the much loof the semitendinosus are in these circumstances contracted to lessthan half their full length. From this it appears that the semimem-branosus and biceps act chiefly in a ligamentous nlanner; and by thelarge number of their short fibres combining to maintain the requiredlength of muscle they have great strength in their action, whetherthey combine with the vasti and crureus to erect the trunk upon thethigh in rising up, or convey the flexing action of the iliopsoas to theknee. The semitendinosus muscle, on the other hand, consisting offibres few in number and with much more slender tendon than thebiceps and semimembranosus, is much less fitted for bearing a greatstrain; but will move the knee quickly through a large area, and inthis will act in company with the sartorius and gracilis.
In the bringing of these remarks to a close, another of the longmuscles of the thigh, the rectus femoris, demands special notice onaccount of the remarkable arrangement of the superior tendon. Per-haps that arrangement, which is by no means peculiar to man, is notto be explained principally by physiological considerations; but it isat least interesting to observe that the advantage of having the fibresrather in medium than in full contraction, gained, as already said, insome long muscles by stretching of the fibres over a joint, is in thisinstance obtained by the peculiarity of the upper attachments. Forif when the thigh is straight the anterior head of the rectus be cut,the muscle will be lengthened at least a quarter of an inch; or ifwhen the thigh is flexed the posterior head be cut, the muscle will inlike manner be lengthened. It is obvious therefore that had onlyone of the heads existed, there would have been a quarter of an inchmore contraction of the muscle required, either in passing from theextended to the flexed or from the flexed to the extended position ofthe hip-joint. To gain that quarter of an inch of shortening withoutcontraction of every fibre to that extent further than is its wont,would require the addition of probably half an inch of muscle; andthat addition would require to be made to every fibre in order to beeffective. The total addition of muscular action thus required wouldbe considerable; and so also, therefore, is the saving of muscularaction caused by the arrangement of the upper heads of origin.
