Recent experimental approaches to the formation of aqueous humor, its composition, and modifications have relied largely on rabbit studies.1-3 In this species an aqueous humor is formed which is more alkaline and contains an excess of bicarbonate and a deficit of chloride as compared with plasma. These findings tended to support the Friedenwald-Kinsey theories as to the secretion of aqueous humor. Knowledge of the composition of rabbit aqueous and the reported presence of carbonic anhydrase in the ciliary body4 led directly to the successful trial of carbonic anhydrase inhibitors, such as acetazoleamide, for suppression of aqueous secretion. In rabbits, tonographic studies revealed that such agents lower intraocular pressure by means of a 50% to 60% suppression of rate of aqueous formation.5 Furthermore, the alterations in composition of the aqueous humor of posterior and anterior chamber3 and turnover of test substances6 are compatible with this degree