320 
air-cushion carrying the heavy head, has been accepted by many 
zoologists. In fact it is very plausible that the inert Orang utan, 
ORANGOETAN 
Fig. 3. Laryngeal sac and cheek-lobes of a large male orangutan 
(reproduced from DENIKER and BourarT). The rather stiff cheek- 
lobes can prop the head sideways on the air-cushion. Slightly 
more than 1/5 of nat. size. 
which is much less muscular than the African iarge Anthropoids, 
which is particularly provided with weak nuchal muscles according 
to the two mentioned, French anatomists and which as it were, 
drops its heavy face on his chest, possesses in the laryngeal sae an 
apparatus to break as by an air brake the shocks to which his 
cranium and its contents, which hangs more heavily forward than 
in the other Anthropoids, but which is less efficiently supported 
by the neck muscles, would be exposed in locomotion ’). 
In the other Anthropoids, which possess a throat pouch, this me- 
chanism is in itself inadequate, so that greater demands are imposed 
on tbe cervical muscles with the nuchal ligament to carry the 
heavy head. But even these, though besides assisted by the air- 
cushions of the (small) throat-pouches, would be inadequate to protect 
the cranium and its contents entirely against dangerous shocks with- 
out the other above-mentioned muscle apparatus. They are supported 
in this task by the apparatus of the occipito-frontalis muscle, the 
musculus epicranius, which is present in all Apes and Man, in 
1) The inion is placed very high, so that the nuchal muscles (and ligament) 
support the head only when it is lifted up by the laryngeal sac. 
