MUSCULAR SYSTEM yt 
and the frequent absence of that to the fifth toe, evidences of a 
retrogressive tendency. 
The special extensors of the fingers ee similar variations, 
being now as a rule restricted to 
the thumb, the index, and the 
little fingers. Occasionally, how- 
ever, the third and fourth fingers 
also receive tendons from the ex- 
tensor minimi digiti,andthe middle 
finger may receive a tendon from 
the extensor indicis proprius. 
The changes brought about in 
the sole of the foot naturally affect 
the dorsum as well. There can 
indeed be no doubt that changes 
have taken place in the extensor 
brevis digitorum of the foot (¢.07., 
Fig. 72) complementary to those 
above described in the flexor digi- 
torum communis brevis. The 
extensor brevis digitorum must 
formerly have arisen higher up 
the fore-leg, and have secondarily © 
shifted downwards to the dorsum 
pedis. The connection demon- 
strated by Ruge between the short 
common flexor of the toes and the 
interossei1 pedis undoubtedly in- 
dicates the “extreme limit of the 
distal wandering of the extensor 
brevis.” 
Ruge has further proved the 
interesting fact that all the seven 
interosse1 pedis at a certain stage 
in the human embryo have a 
plantar disposition, and that they 
shift at a later stage to a position 
between the metatarsals, there to 
divide into the plantar and dorsal 
series. 
wt 
Avda 
ALIN yyw 
Wal Ziti“ SS z ' Ween . = — = 
ZALES = Sis ~ AV WSN = aoe a ————— 
SA ee Z = = ‘ | . —s=s-J — = 
i — ISS ! ANG } = 
= SON | < iis : 
——— a S<SXy | Wi \ ON Wok ST! i PLN 
—-s es S ~~ ee 
z #3255335 =—Z \\ q ‘ SN SS NE N 
ap \\) = SS ee = == Ah — aa Hl — = 
= }}}, , We ce = = SR Lap y) : : —— = 
= ) AU re -- << = al wey 2 7 : 
=n f ” be F ’ = 
= : : S 4 é 1 
——— H - 5 
. f e ss e - S 
‘ S 
< : 
. e . S 
. 
Fic. 72.—SUPERFICIAL MUSCLES AND 
‘TENDONS OF THE DORSUM OF THE 
RicHt Foor. One-third natural 
size. (After Rauber.) 
Gp» tibia 6) fibula = ¢) navieular = 4. ., 
tibialis anticus muscle; ¢.a’., its 
tendon of insertion; e./’., M. extensor 
proprius hallucis (e. hall. long.) ; e.d’., 
M. extensor communis digitorum 
(e. digit. longus) ; ed”., its expan- 
sion and insertion on the second toe ; 
p.t'., peroneus tertius; p.t’”., its 
insertion on the fifth metatarsal 
bone; s:, Me ‘soleus 5765) Mi: 
peroneus brevis; ¢.0., M. extensor 
hallucis brevis ; ¢.07., extensor brevis 
digitorum; J/g. anterior annular 
ligament ; jc., transverse band of 
the dorsal fascial of the foot. 
An exact parallel to this is found in certain Apes (Cebus, 
Cercopithecus) and in most of the lower Mammals, in which 
the interossei have a plantar position throughout life. 
In the 
