64 THE MUSCULAR SYSTEM OF THE FROG. 
forward in the middle line as a stout band nearly 
to the chin: it then enters the tongue, and runs 
back along it to its tip. 
v. The petrohyoid : a set of four muscular bands which 
arise close together from the outer surface of the 
auditory capsule, and diverging from one another 
in a fan-like manner, pass round the flocr of the 
pharynx and cesophagus to be inserted in front 
into the median ventral line of the pharynx, and 
behind into the side of the hyoid. The first 
or most anterior band is a wide thin sheet of 
muscular tissue, while the three posterior por- 
tions are very narrow slips. 
2. Muscles of the side of the head. ¢ 
Remove the skin carefully from the side of the head and jaws, 
noticing how much more closely it 1s attached to the underlying 
parts than was the case in the body. 
a. Depressors of the lower jaw: opening the mouth. 
i. The depressor mandibuli; has been already seen 
and dissected. 
b. Elevators of the lower jaw: shuttingthemouth: these 
lie in the space between the auditory capsule and 
the eye. 
ii, The temporalis: arises from the upper surface of 
the auditory capsule, and passes outwards and 
downwards between the pterygoid and maxillary 
bones and in front of the cartilaginous ring sup- 
porting the tympanic membrane, from which 
some of its fibres arise: it is inserted into the 
coronoid process of the lower jaw. 
ili, The pterygoideus: a slender muscle placed just in 
front of the temporalis and partly covered by it: 
it arises from the side wall of the skull, and is 
inserted into the mandible further back than the 
temporalis and very close to the joint. 
iv. The masseter: a small muscle placed behind the 
temporalis : it arises from the quadratojugal and 
y 
