Rate of entrance of sodium into the aqueous humour of the rabbit.

WITH the advent of the active secretion theory of formation of the aqueous humour, increasing importance has been attached to knowledge of the rates at which the various constituents of this fluid enter the eye (cf. Langham, 1958). This information is required in order to reach some understanding of aqueous humour dynamics and also to assist in elucidating the nature and action of the secreting mechanism. The rates of flow of water and certain solutes through the anterior chamber have been estimated by studying the rates of accumulation or disappearance of Rayopake, Diodrast, or p-aminohippurate (Ba&rany and Kinsey, 1949), fluorescein (Goldmann, 1950; Langham and Wood, 1956), and 24Na (Kinsey and Barany, 1949; Davson, 1955, 1956; Kinsey and Palm, 1955, 1958). Mathematical analysis of some of these findings in terms of transfer coefficients representing entrance into the anterior chamber aqueous by flow and diffusion (kf and kd, respectively) have yielded values ranging from kf= 0-017 0-018 min.-1 (Kinsey and Palm, 1955; Friedenwald and Becker, 1956) down to kf=0 009 min.-' (Davson, 1955; 1956). If the solute concentrations in plasma and aqueous humour and the volume of the anterior chamber are known, it is possible to calculate the rate of solute entering the eye at a steady state, where influx and efflux are equal. In these circumstances the rate at which solute leaves the anterior chamber for the drainage channels depends on the outflow rate and' the anterior chamber concentration;