Evaluation of the results obtained in the study of the effect of cerebrospinal fluid on various physiological systems is complicated by the fact that the composition of the cerebrospinal fluid depends to a large extent on the state of the blood-brain barrier, and thus reflects not only a certain physiological state of the central nervous system. There is no doubt that the metabolic products of the brain, secreted into the cerebrospinal fluid, exert their effect not only on the activity of various parts of the brain and on the coordination of their functions, but due to the rapid transition of these substances from the cerebrospinal fluid into the general circulation, they also affect as a humoral a factor on the function of other physiological systems, as it was revealed in a number of experiments carried out in recent years in our laboratories. For example, it turned out that under various influences (direct irritation of the central nervous system in experimental epilepsy, irritation of the sensory nerves associated with severe pain, traumatic shock, toxemic or chemical shock, as well as starvation, prolonged insomnia, etc.) - substances appear in the cerebrospinal fluid that affect the state and activity of the cardiovascular system, the tone of smooth muscles, the excitability of the central nervous system, etc. These are the results of the work of our employees: Zeitlin, Weiss, Harles, Voskresensky, Gromakovskaya , Bazarova, Gotsman, Komarova and others. Work in this direction continues at the present time.