MEMBRANES OF THE BRAIN. 343 



ly glide eight or ten lines between the laminae of the dura ma- 

 ter, and are somewhat tortuous. This sinus also receives se- 

 veral veins from the bones, and some from the scalp, which 

 traverse the bones at different places: among the largest of them 

 are those that come through the parietal foramina. The-flura 

 mater itself sends some of its' veins into this sinus. 



In the longitudinal sinus, towards its posterior part, is found 

 a considerable but variable number of small granular bodies; 

 some in clusters, others insulated ; and from the size of a pin's 

 head to a line or more in diameter. They are the Glandulse 

 Pacchioni: they have no excretory ducts that have been dis- 

 covered, and it is entirely uncertain whether any specific fluid 

 is secreted from them. These bodies are also to be found on 

 the surface of the dura mater near this sinus; some of them, in- 

 deed, make foramina through the dura mater, and corresponding 

 depressions in the skull. One on each side, larger than usual, 



' and near the parietal foramen, is remarkable for this. 



% 



2. The Sinus Laterales, one on each side, are situated in the 

 base of the tentorium, and follow its course along the grooves of 

 the occipital and parietal bones. They then leave the tentorium 

 and go along the groove in the mastoid portion of the temporal 

 bones to reach the posterior foramina lacera, where they ter- 

 minate in the internal jugular veins. Their shape is ovoidal, 

 instead of prismatic, as the longitudinal sinus is; they are also 

 larger than it. 



The sinus of the right side is very frequently larger than that 

 of the left, and seems to be more a continuation of the superior 

 longitudinal sinus. In some rare cases one of these sinuses is 

 deficient. The lateral and inferior veins of the cerebrum, and 

 the inferior veins of the cerebellum run into the lateral sinuses. 



3. The Sinus Longitudinales Inferior is situated in the falx 

 cerebri just above its concave edge. It is much smaller than 

 the superior, and terminates behind in the sinus quartus. It re- 

 ceives the veins of the falx, and sometimes a few from the cor- 

 responding parts of the hemispheres. 



4. The Sinus Quartus, or rectus, is situated in the tentorium, 

 where the latter is joined by the falx major or cerebri. It is 



