3GO 



MUSCLES OF THE FOOT. 



is the peroneous cxternus. (Seo LEG, MUS- 

 CLES or.) The tendon of this muscle passes 

 behind the outer malleolus, tlien, running 

 downwards and forwards, it enters a groove 

 formed in the os calcis, close behind the pro- 

 minence of the base of the fifth metatarsal 

 bone. It then runs across the sole of the foot, 

 in contact with the bones, to be fixed to the 

 inner cuneiform bone and metatarsal bone of 

 the great toe. The course and situation of the 

 tendon well deserve particular attention in the 

 dissection of the foot. Without some study, it 

 is impossible fully to understand its office, or 

 how essential its action is to the mechanism of 

 progression. If we examine the general form 

 of the foot, we see that the anterior end of it is 

 not square, owing to the comparative length of 

 the toes. These are not of equal length, but 

 are each shorter than the other as we proceed 

 outwards, the outermost of all being the short- 

 est. This part of the foot then is like the end of 

 an oblong, with one angle greatly rounded off. 

 When, therefore, the weight of the body is, by 

 the elevation of the heel, thrown forwards upon 

 the toes, there is necessarily a tendency, in this 

 shape of the foot, to tilt the pressing torce out- 

 wards, whereas if all the toes had been of equal 

 length, the elevation of the heel would simply 

 have thrown the weight directly forwards, the 

 support being equal on both sides of the foot. 

 This tendency outwards, occasioned by the 

 difference in length of the toes, is still further 

 increased by the difference in strength, the 

 largest, the most unyielding support, being on 

 the inner side of the foot, the smallest and the 

 most yielding being on the outer. This then 

 being the construction of the basis of support, 

 some means of counteracting this tendency was 

 necessary to enable us to carry the body directly 

 forwards, even in the simple act of walking, 

 and still more in the more violent exertions. 

 This is accomplished by the peroneus longus, 

 whose tendon, like a girt, passes under the 

 outer edge of the sole, and thus, lifting this, 

 and in some degree turning the sole outwards, 

 throws the weight of the body upon the great 

 toe. This action of the muscle is particularly 

 exemplified in the movements of skaiting. 



The movements of the bones of the tarsus 

 are so distinct and constant that we have clas- 

 sified the muscles which act upon them sepa- 

 rately from those of the ankle. (See FOOT, 

 JOINTS or.) 



The muscles of the great toe are remarkable, 

 as might be expected, for their size and strength. 

 The long flexor is considerably larger than that 

 common to the other toes, and gives to this a 

 slip of its tendon, so that the flexor longus pol- 

 licis does in fact assist in flexing all the toes. 



The general arrangement of all the muscles 

 and tendons in the sole is very curious, and 

 lias a further object than the mere flexion of the 

 toes. The great toe is, as we see, well provided, 

 and it needs this, since it bears the greatest 

 share of the burden of the body in walking, 

 &c. The muscu'ar provision for the other toes 

 is as considerable, and indeed more so, in pro- 

 portion to the size of the toes. There is, 1st, 

 the tlexor brevis digitonim ; 2d, the flexor longus 



Fig. 169. 



1 Flexor accessorius. 



2 Flexor pollicis longus. 



3 Flexor digitorum longus. 



4 Slip from the flexor pollicis longus to the flexor 



digitorum longus. 



5 Lumbricalcs. 



6 Tendon of long flexor. 



digitorum ; 3d, this tendon receives an aux- 

 iliary tendon from the long flexor of the great 

 toe; 4th,themassacarnea; 5th, the lumbricales. 

 There can be little doubt that the use of all 

 these muscles is to give a powerful support to 

 the antero-posterior arch of the foot, to which 

 purpose the mere ligaments would be little 

 equal. But we must admire not only the 

 number and force but the arrangement of these 

 muscles, which are so placed as to act, almost 

 all of them, from the same centre, and there- 

 fore with greater advantage for the object of 

 strengthening the arch. Thus the flexor brevis 

 digitorum lies pretty nearly central in this region, 

 while immediately under it the flexor longus 

 digitorum, running from within outwards, is 

 crossed in the opposite oblique direction by the 

 flexor longus pollicis, and these again are still 

 further checked outwards by the flexor accesso- 

 rius, so that the centre of action of all these mus- 

 cles and of the lumbricales also, which arise from 

 the long flexor tendon, is in the same line as the 

 flexor brevis, which lies over them, and as a 

 support to the great arch of the foot this arrange- 

 ment of the muscular chords must have a pecu- 

 liarly advantageous effect. 



(A. T. S. DtM.) 



For the BIBLIOGRAPHY, sec ANATOMY (IXTIto. 

 DUCTION). 



