132 



sent as a detached slip from the anterior bundle of the tendon of the 

 peroneus brevis. It has never occurred as a detached muscle last year, 

 and its termination has been usually into the extensor aponeurosis of the 

 toe. Sometimes a thin fascial expansion took its place, which, how- 

 ever, lost its individuality before reaching its usual point of destina- 

 tion. 



28. The muscle which Otto has named peroneus quartus (called in 

 my former paper p. sextus) has occurred once in last session, differing 

 in some points from the individual muscles which I have described 

 under the same name before. This muscle was five inches in length, 

 flesh}', and it arose from a distinct line on the fibula, between the 

 origin of the peroneus brevis and the flexor hallucis longus ; passing 

 downwards, it became tendinous, and wound round the back of the ex- 

 ternal malleolus in the same groove as the peroneus brevis, from which 

 it was separated by a fold of the synovial membrane lining the theca ; 

 and, finally, it was inserted into a tubercle on the os calcis, behind the 

 process for the middle slip of the external lateral ligament, posterior to 

 the tendon of the peroneus longus, which crosses it near its termination. 

 This muscle, it will be seen, differs from ISTo. 16 in my former paper 

 in the following points : firstly, in arising behind, and not over the 

 peroneus longus ; secondly, in being inserted into the os calcis, instead 

 of the cuboid bone. 



29. A singular internal peroneo-calcanean muscle, perfectly separate 

 from the normal structures, I have seen in one instance to arise from an 

 oblique ridge, two inches in length, above and behind the external 

 malleolus, and directly below the flexor hallucis longus; from this 

 origin a small penniforni muscle was continued downwards and in- 

 wards, soon ending in a tendon, which passed in the halluceal groove 

 on the back of the astragalus, external to the flexor hallucis tendon, and 

 beneath the sustentaculum tali, to be inserted into the anterior and 

 internal part of that process, near the outer and posterior attachment 

 of the calcaneonavicular ligament. This slip was perfectly uncon- 

 nected to the flexor hallucis, and it is one whose homotypical relations 

 are of considerable interest. I was inclined to regard it at first as a 

 representative of the flexor carpi radialis brevis of Wood ; but from this 

 it differs, in possessing a fibular (ulnar) origin. It has been suggested 

 to me that it might be a palmaris muscle, either brevis or accessories ; 

 but for both of these we have much more distinct homotypes, as we 

 shall see hereafter. Tailing these, we are obliged to seek its upper limb 

 representative elsewhere ; and we will find that the only probable 

 solution of the difficulty is the regarding it as a representative of a 

 muscle otherwise unrepresented in the inferior extremity, namely, the 

 pronator quadratus. In support of this explanation we have the fol- 

 lowing argument : — Both are at the lowest part of the limb ; both have 

 their origins from the lower end of the fibula (ulna) ; while in the. 

 forearm the fibres of the pronator quadratus pass downwards and 

 pollexward ; the fibres of the .anomalous slip run in a direction 

 downwards and hailuxward. In one instance, in the left arm of 



