The Movement of Substances in the Cerebrospinal Fluid.

Abstract

The authors undertook to determine and collate the glucose tolerance curves in 2 loci in the cerebrospinal system and in the blood, in the hope not only of establishing the relations of the absolute sugar levels but also of obtaining data on the movement of the cerebrospinal fluid itself or of substances dissolved therein.

To determine the carbohydrate tolerance curves a healthy adult dog was used for each experiment. After 18 hours' fasting, anesthesia was induced by intraperitoneal injection of sodium amytal (Lilly). With full surgical asepsis both cerebral hemispheres were exposed by a midline trephine opening so that either lateral ventricle could be tapped with a specially made brain needle. A cisternal needle was then introduced into the cisterna magna and left there throughout the experiment. Since the latest modification of Folin's micro-sugar method, 1 using unlaked blood, was used, it was necessary to obtain from each locus only 0.1 cc. of fluid for each determination. After obtaining simultaneously one sample from each point, 20 gm. of glucose were given by vein. Every 15 minutes thereafter for a period of 21/2 hours, samples were taken simultaneously from each locus.

Twenty-two experiments were performed. The following table summarizes the relevant essentials from experiments performed after the technique had been perfected.

The data obtained appear to the authors to warrant the following tentative conclusions. These are derived for the most part from the average figures shown in Table I.

1. The relatively close approximation of the 3 initial sugar levels suggests that under stable fasting conditions the sugar level of the dog's cerebrospinal fluid equals that of the blood.