ANATOMY AND PHYSIOLOGY OF THE BRAIN 355 



the cranial bones by means of its prolongations into 

 the many foramina. It sends in various processes to 

 support and separate the different parts of the brain, 

 and its layers separate to form the cranial sinuses 

 (venous). In the vicinity of the superior longitudinal 

 sinus are to be found, on its outer surface, several 

 glandule Pacchionii. They may also be seen on its 

 inner surface and within the sinus, as well as on the 

 pia mater. 



The processes of the dura include the falces cerebri 

 et cerebelli and the teritorium cerebelli. 



The arachnoid is a similar membrane to that of the 

 cord, and is separated, as in the cord, by the subarach- 

 noid fluid from the pia. In front it leaves a space 

 between it and the pia mater, viz., along the pons 

 and interpeduncular region, the anterior subarach- 

 noid space; and behind, between the medulla and 

 and the cerebellum, is a second interval called the 

 posterior subarachnoidean space. Both are connected 

 with the ventricles of the brain by the foramen of 

 Majendie in the pia mater covering the fourth ven- 

 tricle. 



The pia mater is a very vascular delicate membrane 

 which dips into the sulci and forms the various 

 choroid plexuses and also the velum of the third 

 ventricle. The vessels of the brain run in the pia 

 mater before entering the brain. 



The brain, for purposes of description, includes the 

 cerebrum, cerebellum, medulla oblongata, and pons 

 varolii. 



Medulla Oblongata. The medulla oblongata is a 

 pyramidal body, f to 1 inch long, along its ventral 

 surface, and f inch thick. Its larger extremity is 

 continuous with the pons above; its smaller extremity, 

 directed downward and backward, blends with the 

 spinal cord below. The anterior surface lies on the 

 basilar groove of the occipital bone. 



