THE NERVES. 375 



625. Sinus venosi dura matris. They consist of the internal 

 coat of the vessels, strengthened by fibres of the dura mater, and 

 they have small valves. The sinus of either side are in communi- 

 cation, by means of transverse sinus, with those of the other side, 

 and by vena diploicce. and emissaria Santorini with the external 

 cranial veins. They empty their blood into the V. cephalica (s. 

 jugular.) interna. 



Vencz diploicce are situated between the two tables of the bones 

 of the skull in the diploe, and enter into communication, internally, 

 with the sinus of the cranial cavity, externally with the external 

 veins of the head. In each half of the skull four large branches 

 are found : 



1. Frontalis passes through a small foramen at the incis. supra- 

 orbit, to the V. supraorbit. 



2. Temporalis anterior passes from angul. parietal, anter. to 

 V. temporalis. 



3. Temporalis posterior passes behind and above proc. mastoid. 

 outwards, or opens into sin. transversus. 



4. Occipitalis, the largest, opens, in the neighbourhood of the 

 middle line on the linea semicircul. infer., into the V. occipitalis. 



JEmissaria Santorini are canals which connect the sinus with 

 the external veins, through peculiar foramina in the cranial cavity. 

 The largest passes through for am. mastoid., parietale, and candy- 

 loid. posterius. 



The sinuses which meet together in the torcular Herophili : 



1. Sinus longitudinalis superior, is situated in the superior 

 border of the falx cerebri, receives on either side seven to ten Vv. 

 cerebri super r. from the surface of the brain, and some smaller 

 from the falx 'major, is connected by means of for am. parietale 

 with Vv. occipitaks, by means of for. cazcum (in children), with 

 the nasal veins, and falls from above into the torcular. 



2. Sinus tentorii medius s. quartus, lies at the basis of falx 

 cerebri above the centre of the tentorium, from before to behind, 

 where it opens into the anterior boundary of torcular. It forms 

 the continuation of the V. magna Gakni, which arises from the 

 two Vv. cerebri interni, and receives at the anterior part the 



3. Sinus s. V. longitudinalis inferior. It passes along the 

 inferior concave border of falx cerebri, is narrow, and sometimes 

 absent. 



4. Sinus transversi s. lateraks, a right (usually wider) and a 

 left, passing off* laterally from torcular, and passing in the sulcus 

 transversus, at first on the posterior border of the tentorium, 

 horizontally, then in the fossa sigmoidea downwards, inwards, and 



