4 H. ST. J. BROOKS ON THE 
The first division of the prowimal part, extensor ossis metatarsi hallucis (Fig. 11, 
ab.h.l.), arises exclusively from the fibula. It is inserted into the tibial side of the 
shaft of the first metatarsal bone. The second division, extensor proprius hallucis, 
arises partly from the fibula and partly from the tarsus, and is inserted into the 
phalanges of the hallux. The four remaining divisions are exclusively tarsal in 
origin, and end in moderately long tendons which pass to the four outer toes. Two 
other muscular slips are found in this situation, which are evidently segmented off 
from the short extensor, viz., a small fasciculus of muscle which passes from the 
lower end of the fibula to the tarsus, and a few fibres which arise from the tarsus 
and are inserted into the base of the fourth metatarsal bone.* 
The metatarsal heads are represented by three pairs of muscles which arise 
from the dorsum and sides of the second, third, and fourth metatarsal bones 
respectively, and by a muscle arising from the dorsum and tibial side of the meta- 
tarsal bone of the hallux. The mode of insertion is precisely similar to the inser- 
tion of the metacarpal heads of the short extensor in the fore limb. The fibular 
head of the hallucial pair and both heads of the pair appertaining to the minimus 
are either aborted or absorbed into the proximal parts of the muscle. 
The peroneal nerve passes forwards from the back of the thigh and winds round 
the neck of the fibula lying on the uppermost fibres of origin of the outer sector. 
It then passes under cover of the intermediate sector, and gives off nerves of supply to 
all three sectors. Lower down, it receives a communicating twig from the posterior 
tibial nerve, and then runs under cover of the extensor ossis metatarsi hallucis, 
supplies that muscle, gives twigs to the five bellies of the extensor brevis 
digitorum, including the metatarsal heads, and terminates in cutaneous branches to 
the toes. 
The chief difference between the two limbs lies in the fact that, whereas in the 
fore limb the superficial stratum arises wholly from the radial condyle of the 
humerus (though completely segmented off from the triceps), in the hind limb the 
lateral sectors arise from the bones of the middle segment, and the intermediate 
sector, taking origin from the femur, does so from the fibular (v.e., ulnar) condyle. 
In both of these respects, Hatteria foreshadows the condition in Mammals. The 
intermediate sector shows a reduction in the number of its tendons. On the other 
hand, the tibialis anticus approaches the symmetrical form more nearly than does 
the eat. carpi radialis, by virtue of its insertion into the metatarsus, and more 
particularly by the presence of the tendinous slip (fg. 11, 1) which reaches the 
proximal phalanx. 
* Ecker (Der Frosch) describes two muscles in the frog which appear to correspond to these slips. 
One of these, “m. jlexor tarst posterior,” arises from the outer side of the tibia, and is inserted into the 
dorsal surface of the astragalus (p. 134). The other, “m. extensor dig. V. longus,” arises from the 
calcaneum, and is inserted into the fifth metatarsal bone. An inspection of his figure (Fig. 93) shows 
that these muscles are on the same plane as the extensor brevis digitorum (a muscle which Ecker regards 
as extensor longus digitorum). 
