It has already been observed (Chambers and Cameron, '32 ; Chambers and Kempton, '33) that fragments of the proximal tubules of the chick mesonephros in the explant of a healthy culture become converted into blind, tubular segments, in the Iumina of which phenol red and other dyes are accumulated and retained against a concentration gradient (Chambers and Cameron, '32). It has been shown also (Chambers and Kempton, '33) that the process is retarded at temperatures below that of the body and is completely and reversibly inhibited at 3 to 6ยฐC.
This paper deals with the effects of exposing the cultures to various agents some of which are known to inhibit the normal functions of perfused kidneys, viz., the oxidation inhibitors, HCN (Starling and Verney, '25 ; Richards and Barnwell, '27 ; Scheminsky, '29 ; Robbins and Wilhelm, '33 and Ferrari and Hober, '33) and H,S; nitrogen atmosphere and the narcotics, phenyl urethane (Scheminsky, '29 and Robbins and Wilhelm, '33), and ethyl urethane.
Tissue cultures of the mesonephros of a 9-to 10-day chick were prepared on cover slips in the usual way except that in the preparation of the medium the amount of embryonic juice added to the blood plasma was reduced to a minimum to retard excessive growth. After an incubation of 18 to 24 hours the closed segments of the proximal tubules within * Aided by the International Cancer Research Foundation.