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It is obvious that the insertions and actions of the muscles of 
the toes are the same as those of the hand, but much simplified. 
This is in all probability due to the less specialised movements of 
the digits of the foot. This view is supported by the fact that in 
the baboons dissected, where the feet are used much as the hands, 
I found the arrangement in the upper and lower limbs almost identical. 
The facts here brought forward explain many cases of paralysis 
in the hand and certain conditions in the foot. Thus in the case 
described at the beginning of the paper, the second phalanges of the 
middle and ring fingers could not be extended since the interossei 
were paralysed, but the extensor indicis and extensor minimi digiti, 
being unaffected, could extend the second and third phalanges of 
these fingers. In this case the patient could not flex the first phalanx, 
since the dorsal interossei were inactive. 
In all cases of ulnar injury (14), hyper-extension of the first 
phalanx is a characteristic feature, together with inability to extend 
the 2nd and 3rd phalanges, this latter being most marked in the ring 
and middle fingers. Such a condition is explained by the extensor 
communis only extending the first phalanx, and the interossei and 
lumbricals flexing the first and extending the others (1st and 2nd 
Jumbricals are not affected). Similarly these facts explain the results 
of median injury, flexion of the first phalanx and hyperextension of 
the remainder. 
Hammer-Toe is a common condition of hyperextension of the 
1st phalanx, flexion of the second and hyperextension or flexion of 
the third. The case is partly explained by deficient action of the 
interosseous muscles and probably also of the lumbricals. The cases 
of hyperextension of the third phalanx are most likely brought about 
by mechanical factors rather than by action of the lumbricals, which, 
even in a normal foot, are by no means powerful. Moreover, to sug- 
gest that the extension is caused by lumbricals, is to imply that 
either the long flexor of the toes is deficient in action, or that it is 
overpowered by the lumbricals. The former explanation is not cor- 
rect, and the latter is obviously impossible. It seems certain then, 
that in hammer toe, the lumbricals as well as the interossei are 
passive, but mechanical factors simulate to a certain degree and in 
certain cases, lumbrical activity. It is not suggested that such is the 
whole explanation of the condition of Hammer-Toe. It is necessary, 
however, to consider the factors on which stress has been laid in 
