1762 



HANDBOOK OF PHYSIOLOGY 



NElRiJl'IlYSIOI OCA' III 



Left and neht Sulcus central* 



.nl^rwpntrirular foramina 



supcroq sa&ittal Sinus 



Cisterna chiasmatis 



Cisterna intercruril: 

 Inferior horn 



of laUral ventricle 

 Gslerna pontis' 



Aqueduct of Sylvius 



rorammaof luschka 



Foramen 

 of Monro 



Cisterna ma 



fig. 1. Ventricles and cisterns of the human brain. [From 

 Clara (45) 



foramina (of Monro), with the third ventricle which 

 connects, by way of the cerebral aqueduct (of Syl- 

 vius), with the fourth ventricle on the posterior as- 

 pect of the medulla. The subarachnoid space is the 

 space between the arachnoid membrane and the 

 pia; thus, the pia invests the surface of the brain and 

 cord closely, while the arachnoid remains closely ap- 

 posed to the dura and thus follows the contours of 

 the bony covering. As a result, quite large spaces 

 occur between the two leptomeninges (fig. _> ) , these 

 are traversed by the arachnoid trabeculae connec- 

 tive tissue filaments continuous with the arachnoid 

 membrane and, like ihi\ covered with a single layer 

 of mesothclial cells. Since the outer surface of the 

 pia is also covered with a similar mesothelial layer, 

 the fluid in the subarachnoid space is completer) 

 enclosed by a mesothelial lining. In certain regions, 

 the subarachnoid spares are verv large, in which 



case the) are called cisterns: for example, the cere- 

 l 'i II.11111 dull, iry cistern or cisterna magna, the cis- 

 terna basalis, cisterna ambiens and so on. In man, the 



fourth ventricle is connected with the subarachnoid 

 pace oi the cisterna magna by three foramina a 

 medial opening in the roof of the ventricle, the medial 

 foramen (ol Magendie) and the two lateral foramina 

 i"l Luschka) leading out of the lateral recesses. In 

 animals below the anthropoid apes the foramen of 

 Magendie is absent (36) so thai communication be- 



DURA MATCH 



ARACHNOID NEMBR&NE 



SUBARACHNOID SRiCE 

 S P*A MATER 



ARACHNOID VILLI 



CCWuXNCE OF 

 SINUSES 



fig. 2. Ventricles and subarachnoid space [From Rasmus- 

 sen d8i).] 



tween the ventricles and the subarachnoid spate U 

 entirely by way of the foramina of Luschka. 1 



The study of the mode of formation and circula- 

 tion of the cerebrospinal fluid resolves itself ulti- 

 mately into a Study of the relationship of the fluid 

 with the blood vascular system, and we may prof- 

 itably dwell in some deiail on the anatomical aspects 

 of this relationship. The fluid in the ventricle- is 

 separated from the surrounding neuroglial and nerv- 

 ous tissue by a single layer of ependyma! cells. In 

 specialized regions this ependyma comes into close 

 relationship with the pia to form the choroid plexuses 

 which are essentially outpouching? of highl) vascu- 

 larized pia protruding into the ventricles and covered 

 on their inner aspect by the layer of ependyma, The 

 ependyma] cells covering the plexus, however. In- 

 come sharplv dillerentiated from their neighbors, 

 being more columnar and losing the long processes 



1l1.1t are characteristic of ependyma! cells proper; 



'Tlir tm .iiiici) oi Magendie m m.in has been described .is .1 

 post-mortem artefacl V 1 ording to Ban -'" it is very variable 



in size In the majority of cases it is about it> nun- in area, but 



n in.i\ be so l.irni- .is in obi it er. in- tin 1 00!' of the loi 11 tli ventricle. 



In a few rases it mas be absent. In 20 per rent of apparently 

 normal individuals Aiexandei (2) found the foramina of 

 Luschka absent. 



