Henry L. Bruner 9 
The chief tributaries of the vena jugularis interna are: (a) The 
sinus orbitalis, (b) vena pterygoidea, (c) vena cerebralis media, (d) vena 
tympanica anterior, (e) vena mandibularis, (f) vena cerebralis posterior, 
(g) vena jugularis externa. 
a. THE SINUS ORBITALIS. 
(so. Mext Hie 2s Figg Plate 11.) 
A description of the sinus orbitalis must be to some extent a repeti- 
tion of the excellent account of Weber, 77, who, in fact, has been fol- 
lowed by all later authors. Weber, however, studied the sinus apart 
from the system to which it belongs, for he made no attempt to describe 
its tributaries or its drainage. The development of the sinus orbitalis 
is described by Grosser and Brezina, 95, who, also, observed its relation 
to the vena jugularis interna. 
In Lacerta the sinus orbitalis occupies the space between the bulbus 
and the orbital walls, and surrounds the various structures which extend 
into this space. The sinus reaches its greatest development in the region 
of the rectus inferior and obliquus inferior, whence it spreads through 
the median, ventral, and posterior parts of the orbit. The posterior wall 
of the sinus is a fascia which separates the orbit from the great temporal 
fossa; its median boundary is the septum interorbitale, which the sinus 
follows forward to the fissura orbito-nasalis Gaupp, oo. The floor of the 
sinus is formed immediately by the smooth orbital muscle of Leydig, 72, 
below which lies the m. depressor palpebre inferioris, Weber, 77. The 
sinus follows these muscles into the lower eyelid which it penetrates as 
far as the lower margin of the tarsal plate. 
In the rostral part of the orbit the sinus extends into the membrana 
nictitans, where it communicates with a small sinws membrane nictitantis 
(s. m. n., Text Fig. 2). This sinus lies partly between the tubules of 
the Harderian gland, partly in the non-glandular portion of the lid near 
its free border. 
In a dorsal direction the sinus orbitalis forms an incomplete covering 
for the bulbus, only the posterior part of the sinus rising to the roof of 
the orbit. The median part of the sinus reaches the floor of the cranium, 
and expands laterally as far as the tenia marginalis, a band of cartilage 
which lies in the lateral wall of the cranium (Gaupp, 00). From this 
part of the sinus enlarged capillaries continue laterad above the bulbus 
and communicate with the dorsal portion of the sinus membrane 
nictitantis. 
