Aqueous humor was once thought to be a dialysate of plasma, or to be secreted as such by the ciliary body in a manner analogous to secretion of saliva by the salivary gland. Many observations on aqueous humor, both experimental and clinical, could not be accounted for on the basis of either of these suggested mechanisms of aqueous humor formation. Accordingly, a theory was evolved which envisaged these two processes, secretion and diffusion (dialysis), as taking place simultaneously.*
Recent studies of the chemistry of the posterior chamber aqueous humor3 have provided additional evidence that aqueous humor is formed by at least two processes and, in addition, have shown that there are two kinds of aqueous humor in the eye: one in the posterior chamber, and another, having a different composition, in the anterior chamber. Much more experimentation is required, however, to elucidate fully the general nature of aqueous humor