The aqueous and the vitreous body in the eyeball are under a certain pressure; this pressure, developed within the eyeball, is transmitted to the semielastic sclera, and is called the ocular tension. If one disregards the condition of the sclera one finds that the normal tension is the result of a thermodynamic balance. This balance is maintained by the blood pressure in the capillary arteries and by the osmotic pressure of the blood albumins. The blood pressure causes the filtration of the aqueous, while the albuminous content of the blood lessens this filtrating pressure. The higher, therefore, the hydrostatic capillary blood pressure and the lower the oncotic pressure (the suction of the blood colloids) the greater is the ocular tension. Under pathologic circumstances (glaucoma) this balance is influenced by the osmotic pressure of the aqueous albumin and by the swelling property of the vitreous body. Besides these factors, however,