J. Playfair McMurrich 411 
tally and insert in all five digits into the metatarso-phalangeal fibro- 
cartilages. 
In the third and fourth digits inter-phalangeal muscles, the phalangei 
of Humphry, also occur, passing from the plantar surface of the proximal 
phalanx to the base of the second one. 
The intermetatarsales (Fig. 1, im), extend obliquely across the inter- 
metatarsal spaces from the fibular to the tibial side. They are four in 
number, arising from the tibial sides of the bases of the second, third, 
fourth and fifth metatarsals, and inserting into the fibular sides of the 
heads of the first, second, third and fourth metatarsals in association 
with the fibular slips of the flexor brevis profundus of those digits. 
The lateral plantar nerve is, as I have shown elsewhere, 04, the con- 
tinuation into the foot of the ramus superficialis fibularis of the crus, 
while the medial plantar is the continuation of the ramus profundus. 
In the proximal tarsal region the lateral plantar nerve lies immediately 
upon the fibular border of the fibulare and the medial plantar upon the 
centrale. When the flexores brevi profundi appear they lie between the 
nerves and the bones, and still more distally, after the flexores breves 
medii have appeared, the nerves are situated between these muscles and 
the flexores breves profundi, the medial plantar over the interspace be- 
tween the second and third metatarsals and the lateral plantar over that 
between the fourth and fifth (Fig. 1, mp and Ip). The medial nerve 
gives off branches both medially and laterally, the lateral one meeting a 
medially directed branch from the lateral plantar opposite the inter-space 
between the third and fourth metatarsals, so that it becomes difficult to 
determine from which of the two nerves the branches to the muscles arise. 
It would seem, however, that the lateral plantar supphes all the muscles 
of the fifth digit and those inserting into the fibular side of the fourth, 
while the remaining plantar muscles are supplied by the medial nerve. 
Certain it is that the terminal cutaneous branches of the two nerves are 
distributed in such a way that the contiguous surfaces of the four tibial 
digits are supplied by the medial plantar and those of the fourth and 
fifth digits by the lateral plantar, the lateral surface of the minimus and 
the medial surface of the hallux being supplied by branches which descend 
from the crus. 
This distribution differs materially from that described by Humphry, 
72, for Cryptobranchus. In that form the lateral plantar was found con- 
tributing to the supply of the third and second digits. In amblystoma it 
does not extend tibially beyond the fourth digit, the intermetatarsal be- 
tween the fourth and third digits, for instance, being supplied by the 
medial plantar. 
