366 The Nerves and Muscles of the Leg 
fined anlages in an embryo of 20 mm. (Plate IX, Fig. 6). To the prox- 
imal extremity of each anlage branches are given from the lateral plantar 
nerve. The later stages of development I have not followed out carefully. 
M. adductor hallucis—This arises, as pointed out by Ruge, from an 
anlage at the base of the 2d metatarsal and from here wanders into its 
adult position. The anlage of the muscle is shown in Plate IX, Fig. 6. 
The later development of the muscle I have not followed. According to 
Ruge, 78, the transverse head of the adductor comes from the same anlage 
as the oblique, while Schomburg, oo, considers that the latter muscle 
arises from a separate anlage. According to Poirier the nerves of the 
two portions of the adductor arise from a common trunk which would 
be in favor of Ruge’s view. I have found the nerves arising usually from 
quite distinct branches of the lateral plantar nerve. One nerve enters the 
caput obliquum near the proximal end of the middle third; and the other, 
the caput transversum near its centre. 
Lumbricales. 
In neither embryo CXLIV, length 14 mm., nor in 
embryo XXII, length 20 mm., are the lumbricales clearly differentiated. 
In the latter embryo, Plate IX, Fig. 5, however, the anlage of the lum- 
brical muscle of the 2d toe is just beginning to appear and to it a slight 
nerve twig may be traced from the medial plantar nerve. As pointed out 
by Schomburg the lumbrical muscles appear during the second half of 
the second month as separate anlages near the distal extremity of the 
metatarsal bones and from here wander toward their attachments to the 
tendons of the flexor digitorum longus. The three lateral lumbrical 
muscles were found supplied by the lateral plantar nerve and the medial 
by the medial plantar in 9 out of 10 instances by Brooks, 87, while the 
two medial muscles were supplied both by the medial and lateral plantar 
nerves in one instance. He considers that the lumbrical muscles belong 
primitively to the medial plantar territory. 
5. Development and Innervation of the Muscles Supplied by the Medial 
Plantar Nerve. 
To this group belong the flexor digitorum brevis, abductor hallucis, the 
flexor hallucis brevis and the medial lumbrical muscle. This last has 
been considered in connection with the muscles of the preceding group. 
M. flexor digitorum brevis—This muscle develops comparatively late. 
In the 14 mm. embryo I have been able to determine no distinct signs of 
the muscle. In a 20 mm. embryo (Plate IX, Fig. 5) the anlage of the 
