CEREBRAL LOCALIZATION 173 



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 diag- 

 nosis 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 if the 

 trouble lies below the tentorium. 



REFERENCES. 



GUSHING AND BORDLEY. " Observations on experimentally 

 induced choked disc." Bulletin Johns Hopkins Hospital, 



1909, xx., p. 95. 



HORSLEY. " Optic Neuritis." British Medical Journal, 



1910, i., p. 553. 



HORSLEY AND CLARKE. " The structure and functions of 

 the cerebellum." Brain, 1908, xxxi., p. 45. 



THIELE. " The optic thalamus and Deiter's nucleus." 

 Journ. of Physiology, 1905, xxxii., p. 358. 



ALLEN STARR. " Tumours of the acoustic nerve." Amer. 

 Journ. of Medical Sciences, 1910, cxxxix., p. 551. 



