An instrumental syst.em for continuous automatic colorimetric analysis, 1 he ..Zu toAnalyzer,* has been describedThe unit consists of a proportioning pump for metering reagents and sample. Continuous dialysis of the sample after addition of the reagents is used to achieve separation from interfering materials. The reagent mixture is heated so that the reaction may take place, and then it passes into the continuous flow cuvette of thc colorimeter, where optical densities are measured and a ratio recording is obtained.This system was applied by Ferrari et a1.T to continuous chemical monitoring of blood glucose concentrat ions, and the effect of pharmacological agents on these levels was measured in rabbits. An intravenous iieedle was insert ed into the jugular vein and polyethylene tubing was introduced inside thc needle. The tubing was tied in place and the needle removed. In the same way, a second cannula was then inserted in the vein. The first cathcter used for the continuous removal of blood and the second one, for the continuous infusion of a sedative-anticoagulant medication. The first catheter w a s connected through a variable-speed proportioning pump to the sampling side of the manifold. A second channel of the pump was used for the cont inuous infusion of the sedative-anticoagulant mixture a t the same rate.'This accomplishment suggested a technique for use in human subjects. The purpose of this study was to demonstrate the feasibility of automatic, continuous determinations of blood glucose in patients, and to show the difference between the type of curve resulting and the intermittent measurements in standard use for many years. Materials and MethodsFor this study, it was important to obtain a continuously aiiticoagulatetl sample of blood from the subjects. This wits accomplished by using a modified double-lumen needle. This needle, originally proposed by Duncan A.HoladayJ was made of metal, and modification was required to eliminate its positional sensitivity..4 double cannula was constructed from polyethylene tubing, as illustrated in FIGURE 1. On the side arm of the glass H was attached a length of 0.034 * 'Technicon Instruments Corp., Chauncey, N. Y.t See article elsewhere in this monograph.

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