Charles R. Bardeen 349 
metatarsal, but I have found no such condition in the embryos studied. 
The tendon when differentiated runs toward the fifth digit. The nerve 
supply of this muscle, described above in connection with the extensor 
digitorum longus, serves to support the contention of Gegenbaur that 
the m. peroneus tertius is but a differentiated portion of the extensor 
digitorum pedis longus. It varies greatly in size and is frequently fused 
with the m. extensor digitorum longus. Its tendon may terminate on 
the fourth metatarsal. Rarely a tendon shp is given to the extensor 
tendon of the little toe (Le Double). 
M. extensor hallucis longus. Even at an early stage this muscle may 
be distinguished from that of the m. extensor digitorum longus as Schom- 
burg, 00, has pointed out. Its tendon at first is fused with the tendon 
plate of the extensor digitorum longus (Plate IX, Fig. 1), but soon 
begins to acquire some independence (Plate IX, Fig. 2). 
The nerve of supply in embryos CXLIV and XXII enters the muscle 
near the center of its oblique tibial border. As a rule in the adult the 
nerve approaches the tibial border and passes distally across the oblique 
muscle bundles midway between their origin and insertion. This single 
trunk may, however, be replaced by two or more branches arising inde- 
pendently from the n. peroneus profundus. 
Variations in the muscle are most frequently found with respect to 
its tendon of insertion. The tendon may divide into two or more parts. 
In one instance it has been found sending a slip to the second toe. The 
body of the muscle may be more or less fused with that of the m. extensor 
digitorum longus. 
The extensor hallucis longus is to be looked upon as an especially differ- 
entiated deep portion of the extensor digitorum longus. Occasionally in 
man there is found arising from the fibula a special long extensor of the 
second toe (Gruber, 75). This is homologous with the extensor indicis 
proprius of the forearm. Chudzinski, 74, has described a deep extensor 
sending tendons to the first metatarsal, to the second and third, and to the 
fourth and fifth toes, an arrangement corresponding somewhat to one normal 
in several mammals (marmot, porcupine, beaver, Le Double). Both the 
extensor hallucis longus and the extensor digitorum longus are connected 
with the dorsal tendon plate in the embryo at an early stage. Normally a 
tendon for the first toe develops from the deep surface of this plate in con- 
nection with the extensor hallucis longus muscle, but the variations found 
in the adult show that the primitive tendon plate may be variously subdivided 
during embryonic development. The tendon of the extensor hallucis may 
send a tendon to the first metatarsal or to the second toe, ete. (W. Gruber, 
75)- 
Mm. extensor digitorum brevis—This muscle becomes differentiated 
beneath the extensor tendon plate and is best developed on the fibular side 
