396 THE POPULAR SCIENCE MONTHLY. 



arch or bow at that end, as it is at the opposite one ; if, however, it 

 passed directly across the sole from end to end there would be little 

 if any free space beneath, but, being crossed by the flexor longus digi- 

 torum, which comes round the ankle at a higher level, it is so drawn up 

 that a hollow beneath the arch is formed ; the flexor accessorius, by 

 drawing back the tendon of the flexor longus poUicis, compels it to 

 cross the other nearer to the heel, and so increases this effect. Thus 

 the flexor longus poUicis, regarded as the chord of the arc, becomes 

 itself an arc. 



The tendency to inversion which all these muscles, acting from the 

 inner side of the ankle, might occasion is corrected by the long pero- 

 neal on the outer side ; it also, acting on the base of the first meta- 

 tarsal bone, a point considerably beyond the center of gravity, has a 

 bracing action on the arch, as the weight of the body falls upon it. 

 In this, too, no doubt the small muscles of the sole assist those of the 

 calf, but I can not accept the converse statement that it is the " mus- 

 cles of the sole assisted by the tibial muscles " which " are the active 

 agents." The deep muscles of the calf have much the more potent 

 influence. Thus it is that by the action of muscles the whole of the 

 strain which the weight of the body in walking would otherwise throw 

 on the ligaments binding the arch together is removed, and any tend- 

 ency to flattening of it prevented. 



This, which has been called my " bowstring theory," is the view I 

 put forward in a little monograph, " On the Arch of the Foot," written 

 and printed in 1877. For reasons therein given I could not accept the 

 view that the arch is maintained by ligaments, or believe in the car- 

 riage-spring movement of those ligaments, yielding, to the weight of 

 the body, as the explanation of a springy gait. It is really due to the 

 heel being gently lowered and firmly raised. Upon this the grace of 

 walking depends. On the same grounds I hold that in proper walking 

 the foot does not lengthen. Camper, whose treatise is regarded as 

 classical, but which, as I think, contains many important errors of fact 

 and of induction, said that his knowledge of anatomy taught him that 

 it did so. On the contrary, I believe that as the tightening of a bow- 

 string approximates the ends of the bow, so the bowstring r.ction of 

 the flexor muscles on the arch of the foot tends to shorten it. If walk- 

 ing were a succession of standings, flat-footed alternately on either 

 foot, no doubt there would be lengthening, as the ligaments of the 

 arch yielded. Such a mode of progression is, we know, possible ; and, 

 indeed, we sometimes see something like it, hardly, however, to be 

 called walking. I would ask those who believe that the foot in walk- 

 ing lengthens "one tenth of its length, or about an inch" (a statement 

 on high authority made during the past year), to consider this : What, 

 then, would be the condition of the sole, after a long walk, from fric- 

 tion caused by the necessary sliding with the weight of a man borne 

 upon it ? As in every mile of the ordinary march of soldiers more 



