320 Dr. A. Macalister on the Formation of 
the pollex: these are differentiated fasciculi of the muscles 
utilized for an important special purpose. 
The annularis or ring-finger has in man its palmar radial 
muscle developed as the second palmar interosseus; and the 
palmar ulnar, which arises generally from the unciform bone, 
is shifted in its insertion, into the first phalanx of the little 
finger, and constitutes the flexor brevis minimi digiti. For 
the little finger the radial palmar muscle is developed in man 
and the quadrumana as the third palmar interosseus; and as 
such it exists in the armadillo. The palmar ulnar muscle is 
developed into an abductor minimi digiti in the human hand : 
this fact was first noticed in the case of the Ornithorhynchus, 
by Meckel; but.it will be found equally true in man, the cat, 
and in such of the quadrumana as I have examined. 
The pedes of vertebrate animals, both mammalian and rep- 
tilian, exhibit a corresponding series of muscles. Taking the 
human foot as an example, we find for the tibial side of the 
hallux a muscle, the abductor pollicis, or at least its caleanean 
head, which is found in ingle. many carnivora, and 
marsupialia. On the fibular side a corresponding muscle, the 
flexor brevis pollicis, occurs, a muscle whose single origin 
indicates that it is not the complete representative of its syno- 
nym in the hand. This muscle is absent in some monkeys, as 
the mandril, but large in others, as Macacus. The second toe 
has its tibial muscle circumstanced like its fellow of the manus, 
and is thus modified into the adductor hallucis, a muscle which 
is the undoubted representative of the deep head of the hand 
flexor.. From the fibular side of the second metatarsal we find 
what should be the outer of the plantar muscles modified into 
the first slip of the musculus transversus pedis, and crossing 
the metatarsal bone to be inserted into the outer sesamoid bone 
of the hallux ; the remainder of this transversus is made up of 
the fibular interossei of the third, fourth, and part of the fifth 
uniting and running transversely: its obvious manus repre- 
sentative is the adductor pollicis, to which there is very often 
an accessory fasciculus from the fourth metacarpal superadded, 
as noticed by Huxley (loc. cit. p. 538). The tibial interosseus 
of the third, fourth, and fifth toes remain in man unchanged, 
as the first, second, and third plantar interossei respectively ; 
of these the two last named exist in Cercopithecus and Macacus, 
but the first in these animals is either prolonged as a rudiment 
of the transversus pedis or absent altogether. The flexor 
brevis minimi digiti is made up of the remainder of the last 
fibular muscle that is not required for the transversus. 
The plantar interossei having thus been accounted for in 
man, it only remains to refer to their types the muscles in those 
