M76 A MANUAL OF ANATOLI Y 



backwards. Its tributaries are derived from the lower part of 

 the falx cerebri, and from the adjacent parts of the mesial surfaces 

 of the cerebral hemispheres. 



The straight sinus is situated at the junction of the falx cerebri 

 with the tentorium cerebelli, and is formed by the union between 

 the inferior longitudinal sinus and the vena magna Galeni at the 

 anterior margin of the tentorium. It is triangular, and increases 

 in size from before backwards. Its course is downwards and 

 backwards in the median line to the left side, as a rule, of the 

 internal occipital protuberance, where it becomes slightly dilated, 

 and is continued into the left lateral sinus. Its terminal dilatation 

 is connected with the torcular Herophili by a transverse vessel. 

 In those cases where the superior longitudinal sinus passes into the 

 left lateral sinus, the straight sinus passes into the right lateral 

 sinus. In addition to the inferior longitudinal sinus and the 

 vena magna Galeni, the straight sinus receives some of the superior 

 cerebellar veins and tributaries from the falx cerebri and tentorium 

 cerebelli. 



The lateral sinuses are two in number, right and left. Each 

 sinus extends from the internal occipital protuberance to the 

 postero-external compartment of the jugular foramen, through 

 which it passes, to terminate in the bulb of the internal jugular 

 vein. The sinus pursues a curved course. It passes outwards 

 in the transverse groove on the inner surface of the tabular part 

 of the occipital bone as far as the inner surface of the postero- 

 inferior angle of the parietal bone. Here it ascends for a little 

 in a groove, and, having described a sharp curve, it passes down- 

 wards and inwards in the sigmoid groove on the inner surface of 

 the mastoid portion of the temporal bone. Finally, it turns for- 

 wards in the groove on the upper surface of the jugular process of 

 the occipital bone to the jugular foramen. As far as the postero- 

 inferior angle of the parietal bone the lateral sinus is contained 

 within the attached border of the tentoriimi cerebelli, and, just 

 before leaving this, it receives the superior petrosal sinus. The 

 right lateral sinus is, as a rule, foimed by the superior longitudinal 

 sinus, and, in these circumstances, is larger than the left, which 

 is usually formed by the straight sinus. The reverse, however, 

 may be the case. As stated, the torcular Herophili and the terminal 

 dilatation of the .straight sinus are connected by a transverse 

 branch. 



The lateral sinus of each side, in addition to the superior petrosal 

 sinus, receives tributaries from the posterior part of the cerebrum 

 and the superior and inferior surfaces of the cerebellum. It also 

 receives the posterior temporal and occipital diploic veins, and 

 the petro-squamous sinus, when that sinus is present. Near its 

 termination it communicate? with the marginal sinus of the same 

 side. The sinus communicates with extracranial veins by means 

 of two large emissary veins, posterior condylar and mastoid, 

 which pass through the corresponding foramina. These foramina. 



