CIRCULATORY SYSTEM OF THE GRASS-SNAKE. 641 



III. A vein that joins it at the anterior end of the orbit and 

 forms an anastomosis between it and the orbital sinus. 



IV. An Inferior Palpebral Vein (Y. palpebralis inferior, Bruner) 

 that also enters at the front end of the orbit and runs backwards 

 in the lower eyelid to its posterior end, where it enters the orbital 

 sinus together with the superior palpebral vein. 



V. Several small veins from the orbital sinus just posterior to 

 the orbit. 



VI. An Oblique Palatine Vein (V. palatina obliqua, Brunei') 

 that runs obhquely forward beneath the skull at the level of the 

 hypophysis to join the similar vessel of the opposite side and form 

 a median palatine sinus which runs forward for a short distance. 

 Before reaching the middle line it gives off a palato-cerebral 

 vein. 



The Palato-cerebral Vein (V. palato-cerebrales, Bruner) runs 

 dorsally around the skull and enters the median cerebral 

 vein soon after this leaves the cranium. 



The Orbital Sinus (Sinus orbitalis, Bruner) is a fairly large well- 

 defined sinus occupying the inner and hinder parts of the orbit. 

 At the outer end of the hinder part it is prolonged outside the 

 orbit beneath the Harderian gland. It receives the following- 

 branches :-^ 



I. A small vein at its anterior end which comes from the nasal 

 gland. 



II. The vein joining it to the maxillary vein which also enters 

 at the anterior end. 



III. The Siiperior Palpebral Vein (V. palpebralis superior, 

 Bruner), which arises at the anterior end of the sinus and i-uns 

 backwards in the upper eyelid, re-entering the sinus at its 

 posterior end and receiving just before it does so the inferior 

 palpebral vein. 



IV. The Secondary Anterior Cerebral Vein (Sekundare Verbind- 

 ung der v. cerebralis media mit der v. cerebralis anterior, Grosser 

 und Brezina) which runs from the posterior internal corner of the 

 orbital sinus backwards inside the skull into the median cerebral 

 vein just as the latter is leaving the ci-anial cavity. The anterior 

 segment of this vessel is formed by a part of the original anterior 

 cerebral vein. 



The Lateral Cephalic Vein (V. capitis lateralis. Grosser und 

 Brezina ; V. jugvilaris interna, Bruner) arises from the posterior 

 prolongation of the orbital sinus and runs inwards and backwards 

 to the side of the internal carotid artery. It passes backwai'd 

 closely accompanying this aitery to the posterior end of the head, 

 where it bends round to the ventral side and unites with the 

 maxillary and mandibular veins to form the common jugular vein. 

 On its course it receives : — 



I. A vein from the Harderian gland. 



II. The Median Cerebral Vein (V. cerebralis media, Bruner), — 

 This runs from the longitudinal cerebral vein on the dorsal side 



