CEREBRAL LOCALIZATION 237 



THE CEREBROSPINAL FLUID. 



This fluid is clear, watery, and of low specific 

 gravity ; it contains almost no albumin, but some 

 sugar. Until recently this reducing substance was 

 thought to be a pyrocatechin body. It contains no 

 cells in health, nor does it contain the antitoxins, 

 opsonins, or alexins which are present in plasma, 

 lymph, and most serous fluids. This explains the 

 great liability to septic meningitis after injuries to 

 or operations on the central nervous system. As 

 urotropin is excreted into the cerebrospinal fluid 

 when given by mouth, it may usefully be administered 

 to prevent septic complications such as the above, 

 or following on suppurative otitis media. Some 

 success is already claimed for this procedure. 



The fluid is secreted by the choroid plexus into the 

 lateral and third ventricles ; it passes by the Sylvian 

 aqueduct into the fourth ventricle, escapes by the 

 foramina in the roof into the subarachnoid space, 

 and is absorbed, partly by the aid of the Pacchionian 

 bodies, into the superior longitudinal sinus and other 

 veins. Hydrocephalus is produced by blocking of 

 the foramina in the roof of the fourth ventricle. If 

 an exit is provided, large quantities of cerebrospinal 

 fluid may be lost daily. 



Lumbar puncture is a very valuable aid to dia- 

 gnosis in various forms of meningitis, parasyphilitic 

 affections, etc., and the fluid may be blood-stained 

 after cerebral haemorrhage or injury. It is also 

 valuable in treatment as a means of reducing intra- 

 spinal and intracranial pressure, particularly it the 

 trouble hes below the tentorium. 



