The pathology of the cerebrospinal fluid in cases of tuberculous meningitis has been the object of intense study in recent years. However, the diagnostic value of examinations of that fluid simply by chemical and cytologic methods is of only relative importance. The most reliable test is to find tubercle bacilli in the cerebrospinal fluid; but that is microscopically often so difficult that in most cases no satisfactory result can be obtained. Consequently, the necessity arises of performing animal injections to confirm the diagnosis. But it is well-known that a comparatively long time, even more than three weeks, is required to determine the result of the experiment. For this reason the method has been abandoned. It is also well known that the presence of the tuberculosis organism produces three kinds of reaction to tuberculin injection, namely, (1) general reaction, (2) focal reaction and (3) local reaction. The focal reaction may well