J. Playfair McMurrich 433 
Brooks’, 87, observations on the innervation of the lumbricals show that a 
confusion of the constituents of the two plantar nerves may occur, similar 
to that which may obtain between the ulnar and median in the hand. 
A word concerning the origin of the flexor brevis hallucis may not be 
out of place. In certain English text-books, Morris, 3d Ed., and Cun- 
ningham for example, it is stated to arise in part from the cuboid bone. 
This may possibly represent its physiological origin, but it certainly 
gives a very incorrect idea of its morphological relations. It is very 
clear from the study of fetal preparations that the muscle has its origin 
primarily from the first cuneiform and secondarily from a dense lamella 
of connective tissue which forms a sheath for the tendon of the flexor 
longus hallucis and proximally is continuous with a dense fascia cov- 
ering the tendon of the peroneus longus and also with a strong liga- 
ment which extends from the navicular to the third cuneiform. It is 
through its connection with the peroneal sheath that the muscle reaches 
Fic. 9. Diagram to show the constitution of the interossei in the human 
foot. fbp=—flexor brevis profundus; im =intermetatarsal; /-V = metatarsal 
bones. 
the cuboid, but it is a mistake to suppose that this bone forms part of 
its true morphological origin. 
The lumbricales are, as in the hand, clearly representatives of the 
flexor brevis medius stratum superficiale of the lower forms. And, 
similarly, both portions of the adductor hallucis are portions of the 
flexor brevis medius str. profundum, Ruge’s, 78, observations on the 
development of the caput transversum, apart from comparative studies, 
showing its embryological relations to the caput obliquum. Meckel’s, 
32, identification of the caput transversum as a lumbrical is unsup- 
ported by either embryological or comparative evidence. 
The interossei resemble closely those of the hand, whose phylogeny I 
have already, 03, considered. They represent a combination of the 
flexores breves profundi and the intermetatarsales, and their constitu- 
tion may be understood from the accompanying diagram (Fig. 9). 
Considering first the three central digits; each possesses two slips of 
the flexor brevis profundus. Both slips of the second digit unite with 
