THE PLANTAR ARCH 199 



to the scaphoid bone, and the tibialis anticus becomes inserted anew 

 into the internal wedge-shaped and metatarsal bones. " Both of 

 these muscles, thus modified, help to maintain the arch of the foot. 

 So does the taisal part of the tendon of the tibialis posticus. 1 " 

 (Keith). 



The three peronei muscles, especially the new peroneus tertius, 

 attached to the little toe, are called in by increased walking to 

 redress the balance of forces in the foot and produce that eversion, 

 with some supination, which is essential to the arch. No arch was 

 possible till these muscles came into some preponderance of action 

 over the flexors, so beloved of gorilla C. The short flexor of the 

 digits becomes modified so that its attachment to the tendons of 

 the long flexors in the sole has its origin completely transferred 

 to the heel-bone in man (Keith). ' ; It can thus act more powerfully 

 in maintaining the arch," and finall}- the^ea-or accessorius, a muscle 

 which cannot fail to surprise the dissector when he first penetrates 

 into the deep layer of muscles of the sole, and which is a detached 

 piece of the long flexor of the great-toe, becomes especially well- 

 developed and helps to maintain the arch. 



The order of events then is : first, increased and altered muscular 

 function ; second, growth of bones and adjustment ; third, binding 

 together of these by new or modified ligaments. If it were pos- 

 sible to separate in this way the age-long formation of such a 

 living tool as the human foot, this is the order in which alone, I 

 submit, the sequence of events can be placed. It is a convenient, 

 because simple and plain example of initiative in evolution, and 

 I cannot say how much I owe to Professor Keith's teaching on the 

 subject. 1 



1 It is not sufficiently noticed by some writers how important is Pro- 

 fessor Keith's teaching as to the maintenance of the arch by muscular action 

 rather than ligamentous union. And it is a very practical matter from my own 

 point of view in connection with the prevention of flat-foot in the young. If 

 indeed the poor deformed feet of the sufferers can only be corrected by 

 attention to the lowly-organised ligaments, and the muscles will not avail, 

 I can but add " God help them ! " 



