4 
436 The Phylogeny of the Plantar Musculature 
6. The mammalian flexor brevis hallucis is a compound muscle; its 
medial head is derived from the flexor brevis superficialis and its lat- 
eral head from the flexor brevis medius stratum superficiale. 
?. The flexor brevis superficialis stratum profundum is represented 
in the human foot by a muscle bundle and tendon which unites with 
the slip of the flexor brevis digitorum passing to the third digit. 
8. The flexor brevis digitorum is not a crural muscle which has sec- 
ondarily descended into the planta. It is from the beginning an in- 
trinsic muscle of the foot. 
9. The flexor brevis quinti digiti is not equivalent to any portion of 
the flexor brevis hallucis, but is a portion of the flexor brevis profundus 
layer. 
10. The oblique and transverse heads of the adductor pollicis are 
primarily parts of a single muscle and are portions of the flexor brevis 
medius stratum profundum. 
11. The opponens hallucis is probably a derivative of the oblique 
head of the adductor hallucis; the opponens quinti digiti is a portion 
of the flexor brevis quinti digiti and therefore a portion of the flexor 
brevis profundus. 
12. The dorsal interossei are formed by the fusion of portions of the 
flexor brevis profundus with the intermetatarsales, the plantar interossei 
being formed by the remaining portions of the flexor brevis profundus. 
ANATOMICAL LABORATORY, UNIVERSITY OF MICHIGAN, 
January 11, 1907. 
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Biscuorr, T. L. W., 70.—Beitrage zur Anatomie des Hylobates leuciscus. Abh. 
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Brooks, H. Sr. J., 87.—Variations in the nerve supply of the lumbrical mus- 
cles in the hand and foot, with some observations on the innervation 
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Brooks, H. Sr. J., 88.—On the short muscles of the pollex and hallux of the 
anthropoid apes with special reference to the opponens hallucis. 
Journ. Anat. and Phys., XXII, 1888. 
Cougs, E., 72—The osteology and myology of Didelphys virginiana. Mem. 
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CRUVEILHIER, J., 77—Traité de l’Anatomie. 3me Edn, Tome I, 1877. 
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Phascogale (Phascogale calura). Journ. Anat. and Phys., XII, 1878. 
