94 The Cephalic Veins and Sinuses of Reptiles 
the relation of the fibers in Text Fig. 16, where the fibers are attached 
chiefly on the median side of the jugular vein. 
The anterior half of the constrictor muscle is very strong in Emys and 
the jugular vein is closely invested by the mass of muscle fibers. The 
function of this part of the muscle is indicated in Fig. 16, where the 
jugular vein is compressed by the contracted fibers. 
The posterior half of the m. constrictor ven jugularis interne (m. c. 
j. i., Text Fig. 17) occupies a position corresponding to that of the con- 
strictor muscle of the lizard. .The fibers of this part of the muscle arise 
in part from the parotic process (processus squamosus of Bojanus), in 
part from the tendon of the m. sterno-mastoideus (capiti-plastralis of 
xX. 
MM Canny wphay 
Fic. 17. Transverse section through the posterior part of the m. con- 
strictor vene jugularis interne of Emys europea. X 15. 
m. c. j. i., mM. constrictor vene jugularis interne; the muscle here includes 
two rather regular layers of spiral fibers. m. s. m., tendon of m. sterno- 
mastoideus; IX, glossopharyngeus; Xg., posterior part of ganglion superius 
vagi. 
Fiirbringer). From their origin the fibers extend toward the vena 
jugularis interna, some passing above, some below the vein, about which 
they wrap themselves in a spiral direction running backward from their 
origin. Longitudinal fibers also occur, chiefly inside of the spiral fibers. 
In a specimen of Emys europea with carapace 16 cm. long the pos- 
terior part of the constrictor muscle envelopes the vein for a distance of 
about 2.5 mm. and includes seven or eight layers of fibers. 'The entire 
muscle has a length, measured on the vein, of 5.4 mm. ‘The vena cere- 
bralis posterior breaks through the posterior half of the muscle to reach 
the jugular vein. 
The anterior part of the m. constrictor vene jugularis interne is 
closely related to the m. dilatator tube of Bojanus, 19-21, whose posterior 
