458 E. C. MacDowell. 
The baboon (fig. 5, B) shows a greater complexity in the arrange- 
ment of the bellies of the flexor digitorum brevis. In general, it 
arises from the plantar fascia covering the caleaneus, and from 
the tendons of the flexor digitorum longus and hallucis longus. 
The first belly arises from the palmar fascia and is situated near 
the heel. Its tendon is long and slender and is inserted as a per- 
forated tendon into the second digit. The second belly arises 
from the plantar fascia further from the calcaneus than the first. 
It swells out as the first one tapers down to receive its tendon. 
Before its insertion into the third digit the tendon from this 
second belly is connected by a ladder of muscle fibers to the per- 
forating tendon of the flexor hallucis longus which lies directly 
below this. The third belly comes partly from the tendon of the 
flexor digitorum longus for the fifth digit, and partly from the 
tendon of the hallucis longus for the fourth digit. ‘This belly 
lies far out from the heel and thus has but a short tendon. The 
fourth belly has its origin on the tendon of the flexor digitorum 
longus and in the intermuscular septa between it and the neighbor- 
ing muscles. This belly is nearer the digits than the third belly. 
The flexor digitorum brevis acts more as a set of accelerator 
for the long flexors than as an independent muscle from the cal- 
ecaneus. However MeMurrich (’07) says that this is anintrinsic 
muscle, which is homologus with the main mass of theflexor 
brevis superficialis str. superficiale. The greater part of its fibers 
arise from the tendon of the flexor longus. It may be noticed 
that this corresponds to the condition found in the chimpanzee, 
although there was no origin from an hallucis longus tendon. 
Champneys describes a muscle in his chimpanzee which is even 
more complicated than the one I describe. Owen and Beddard 
found more simple ones in their orangs. The latter found but 
three tendons. Primrose found four, of which the tendon for the 
third digit was thestrongest; those to the fourth and fifth toes were 
extremely small. The divisions for the fourth and fifth digits 
arose as in my chimpanzee, largely from the tendon of the flexor 
digitorum longus. 
All the short muscles of the hallus and pollex are found in both 
forms with but slight variations from their human homologues. 
