112 THE STRUCTURE OF MAN 



Chimpanzee and Gorilla they are not so markedly dorsal in 

 position as in Aides, Inuus, and the Orang ; the latter therefore 

 are, in this respect, the nearest to Man. 



The adductor hallucis with its caput obliquurn and trans- 

 versum [usually described as a distinct muscle, the transversus 

 pedis] originally forms one mass ; this points back to the time 

 when it was more strongly developed, and when the great toe was 

 capable of more extensive movement (cf. ante, p. 85). The fifth 

 toe also once moved more freely, as is indicated by the opponens 

 minimi digiti, which is only secondarily differentiated during 

 embryonic life from the mass of the flexor brevis minimi digiti. 

 The former muscle is, comparatively speaking, much stronger in 

 embryonic life than later, when it may entirely disappear. 1 



MUSCLES WHICH APPEAR OCCASIONALLY, AND MAY BE 

 CONSIDERED ATAVISTIC 



In dealing with this group of muscles, we may confine our- 

 selves to those which point back to lower grades of organisation, 

 through which the ancestors of Man may have passed phylogene- 

 tically. I wish to insist on this, since nothing is gained by 

 simply labelling muscles " theromorphic," and since, in my 

 opinion, in dealing with such muscles, Testut and certain other 

 authors have exceeded the bounds of moderation. 



One of these apparently atavistic muscles, the cleido-occipitalis, 

 which forms a connecting tract between the trapezius and the 

 sterno-cleido-mastoid, has already been mentioned (ante, p. 102). 

 To the same category belong certain muscle bundles which here 

 and there partly fill up the interval between the pectoralis 

 major and the latissimus dorsi. A typical example of these has 

 been lately described by my pupil Endres (Anat. Anzeiger, Bd. 

 viii. p. 387), the morphological significance of the so-called 

 Langer's arch being incidentally discussed. 



A muscle which very rarely occurs in Man is the latis- 



(Isimo-condyloideus (dorso-epitrochlearis of French authors), an 

 appendage of the latissimus dorsi, branching off from the 

 latter shortly before it is inserted into the humerus. From 



1 The opponens minimi digiti seems to attain development only in the Chim- 

 panzee among Anthropoids. [Incidentally to this topic and to that of the reduc- 

 tion and co - ossification of the penultimate and terminal phalanges of the little 

 toe (cf. ante, p. 89), it is interesting to observe that the muscles of the little toe 

 are more reduced in the higher Apes than in Man.] 



