Sir.—The report "CSF Cytology in the Neonate" by Pappu et al (Journal 1982;136:297-298) emphasizes the importance of cytologic evaluations of neonatal CSF using a slow-speed cytocentrifuge technique. The authors warn against one of the limits of the method, ie, blood contamination of samples. Delay in laboratory procedures, because of CSF hypo-osmolality, and the kind of sampling material, such as glass tubes, can also produce significant impairment of results. In our experience,1,2 laboratory procedures were started within ten minutes after lumbar taps, and my colleagues and I think that it should never exceed a half hour.
The predominant cells in nonbloody CSF collections of neonates are histiomonocytes.1 However, the term "macrophage" should be used with caution and, according to Oehmichen,3 should be restricted to monocytic cells in which the vacuolar content is precisely identified. Then, macrophages can be divided into a few subclasses: true lipophages, erythrophages, and