' 
~ 
Henry L. Bruner i 
from the pila accessoria of Gaup, 00, a transverse cartilaginous rod (‘P. a., 
Fig. 1, Plate IL), which lies in the cranial wall dorsal to the ramus oph- 
thalmicus V. Some of the lateral fibers of the muscle arise from the fascia 
which forms the posterior wall of the orbit. From its origin the m. pro- 
trusor oculi accessorius bends first ventrad, around the posterior part of 
the bulbus, then rostrad below the sinus orbitals, where it lies under the 
m. depressor palpebre inferioris and lateral to the anterior part of the 
m. protrusor ocuh. Below the bulbus the fibers of the m. protrusor 
oculi and m. protrusor oculi accessorius terminate in a single fascia, 
which lies in the floor of the sinus orbitalis. 
The m. protrusor oculi accessorius is innervated by fibers from the 
ramus ad m. depressorem palpebre inferioris, a branch of which nerve 
passes from the m. protrusor oculi into the accessory muscle, where the 
two muscles lie side by side on the postero-ventral aspect of the bulbus. 
The function of the m. protrusor ocul accessorius is similar to that of 
the anterior part of the m. protrusor oculi; it presses against the sinus 
orbitalis from behind and elevates the fascia which forms the floor of 
the sinus. 
The m. protrusor oculi accessorius has been observed only in Monitor 
niloticus and Platydactylus mauritanus. In the latter the muscle is 
very strong, the dorsal attachment extending forward as far as the junc- 
tion of the tenia marginalis with the solum supraseptale. 
The innervation of the m. protrusor oculi accessorius indicates an 
origin either from the m. protrusor oculi or from the m. depressor pal- 
pebre inferioris. 
B. DISTENSION OF VEINS AND SINUSES AND ELEVATION OF BLOOD- 
PRESSURE IN THE HEAD OF SAURIA. 
The immediate function of the m. constrictor vene jugularis interne 
is indicated clearly enough by its structure and relations; it has also 
been repeatedly demonstrated experimentally, both by direct stimulation 
and by stimulation of the nerve. As previously stated, the muscle in- 
cludes both circular and longitudinal fibers. During the contraction of 
the muscle, therefore, two different movements may be seen: a constriction 
of the vein by the circular fibers and a longitudinal contraction of the 
vein by the longitudinal fibers. On account of the former the lumen of 
the vein is closed, the blood current is interrupted and the vein becomes 
pale and colorless. The longitudinal fibers close the mouths of the tribu- 
tary veins and thicken the wall of the vena jugularis interna, thus facili- 
tating the work of the circular fibers. 
