90 The Cephalic Veins and Sinuses of Reptiles 
as a result of which the meeting points of the great cephalic veins have 
been shifted caudalward. This involved a corresponding change in the 
position of the muscle, which lost at the same time its skeletal attachments. 
B. DISTENSION OF THE VEINS AND SINUSES. 
No observations have been made on the flooding of the cephalic veins 
and sinuses of the Ophidia under natural conditions. The court plaster 
method has been employed with different species, but without suc- 
cess. On the other hand, artificial obstruction of the two ven jugulares 
interne produces protrusion of the eyes, enlargement of the sinus vestibuli 
nasi, and other phenomena of like nature. There is, therefore, no doubt 
in regard to the general effect of the contraction of the m. constrictor 
vene jugularis interne. 
Fig. 14. Section of the m. constrictor vene jugularis interne of Hydrophis 
hardwickii. X 50. 
The inner fibers (i.) of the muscle are longitudinal in direction, the outer 
fibers (s) are spiral. The vena jugularis interna (v. j. i.) is much constricted. 
Whether this muscle is assisted by other muscles in raising the blood- 
pressure in the head is a question which must be left undecided. It is 
not impossible that an extraordinary blood-pressure may be produced by 
compression of the larger veins and sinuses after contraction of the con- 
strictor muscle. Such an effect would apparently follow certain move- 
ments of the skeletal parts (palato-quadratum, maxillare, and the quad- 
rato-squamosum), or it might be produced by the elevation of the floor 
of the mouth and tongue against the sinus palatinus and the vena maxil- 
laris, both of which lie close to the oral mucous membrane. Higher 
blood-pressure, under the conditions mentioned, would also probably fol- 
low the contraction of the m. temporalis (m. parietali-quadrato-mandi- 
