A rise in the cell count is encountered in infection of the nervous system, lymphocytes being the predominant cell in virus infection, neuyrosphilis, tuberculoses meningitis and disseminated sclerosis. Poluymorphonuclear leucocytes, whereas in chronic lesions a lymphocyutosis is more usual. A marked increase in the cell count gives a turbid appearance other cerebrospinal fluid. a rise in the prote9incontent of the cerebrospinal fluid occurs in man by conditions. An increase form the normal figure of 20-45 mg to several hundred milligram’s per100ml maybe present in fluid below the level of a spinal tumour which is causing a block of the cerebrospinal fluid pathway, and also in the presence of neuyrofibromata of the spinal of or the auditory nerves, the rise in protein associated with other cerebrospinal lesion is of much less degree, not usually exceeding 100mg per100ml the glucose content of the cerebrospinal fluid is raised in diabetes mellitus. It is reduced in phylogenic meningitis and intuberculus meningitis, in which disease it is a valuable diagnostic and prognostic sign. The chloride content of the cerebrospinal fluid is reduced in any condition associated with a low blood chloride level. The presence of organisms in the cerebrospinal fluid can be detected by bacteriological examination and is an important part of the investigation of a suspected infection of the nervous system.