To the Editor:—
Blood in the cerebrospinal fluid in the absence of a traumatic lumbar puncture is always abnormal. Textbooks do not reveal studies correlating the concentration of red blood cells and the macroscopic appearance of the spinal fluid. This information is of importance when the physician must decide on therapy or emergency diagnostic procedures such as arteriography before the official laboratory enumeration of cells is known. A guide, however imprecise, which estimates cell counts at the bedside will give the physician useful information.
Serial dilutions of fresh whole blood were made in human cerebrospinal fluid which contained no cells, a protein value of 23 mg/100 ml and a glucose value of 88 mg/100 ml. Two tubes of plain cerebrospinal fluid and one tube of distilled water served as controls. The tubes were randomized according to a table of random numbers. Seventeen residents at the Neurological Institute of New