THE CISTERNS in 



The cisterna interpeduncularis (basalts) lies over the inter- 

 peduncular fossa and it contains the third, fourth and sixth 

 cerebral nerves, and the optic tracts in a part of their course. 

 In basal meningitis, purulent exudates are found in the 

 cisternae and, when the cisterna interpeduncularis is im- 

 plicated, ocular paralysis or visual disturbances are of common 

 occurrence. 



The cisterna fossce latcralis cerebri lies in relation to the 

 anterior perforated substance (p. 16) and contains the middle 

 cerebral artery. It is through this cisterna that the purulent 

 exudate spreads to the lateral surface of the brain in tuber- 

 culous bjsal meningitis. 



The cistern i cerebello-medulLiris (c. inagnd] lies between 

 the cerebellum and the lower part of the roof of the fourth 

 ventricle. In this region the roof is extremely thin and con- 

 sists of ependyma and the covering pia mater. The cisterna 

 cerebello-medullaris communicates with the interior of the 

 ventricular system through three small foramina, which 

 pierce the thin roof and, as a result of these communi- 

 cations, the cerebro-spinal fluid (p. 23) is able to drain away 

 into the subarachr.oid space. When the foramina are closed 

 by adhesions, as may happen following meningitis, this outlet 

 is shut off and the fluid accumulates within the ventricles, 

 giving rise to acquired hydrocephalus. It is also owing to 

 these communications that turbulent fluid is frequently found 

 inside the ventricles in association with the presence of puru- 

 lent exudates in the subarachnoid space. 



A small, unnamed cisterna lies over the " cerebello-pontine 

 angle" (p. 22) and it is traversed by the fifth, seventh and 

 eighth cerebral nerves. This cisterna is a favourite site for 

 purulent exudations in cerebro-spinal meningitis, and, there- 

 fore, paralysis of the nerves mentioned is a not uncommon 

 sequela of the disease. 



The Cranial Blood Sinuses are placed between the serous 

 layer of the dura mater and the endo-periosteum of the skull. 



