It has been reported by White and Stam that the equilibrium water content of human hair is decreased by the application of a tensile stress. This result is shown to be inconsistent with general thermodynamics, which predicts an opposite effect in the case when liquid absorption is accompanied by longitudinal extension, as it is in hair. Experiments with horsehair, in which the water content in the stressed and unstressed states, at 75.5per thousand relative humidity, was determined by weighing, showed a small increase in water content on applying a tensile stress, the effect amountingto 0. 28per thousand on the dry weight for a stress of 482 kg/cm². This increase was in quantitative agreement with the thermodynamic theory. Subsidiary measurements of dimensional changes accompanying the application of tension indicated a small increase of volume of the amount to be expected from theoretical considerations. Data are also presented for the length changes which accompany water absorption, and for the water absorption as a function of relative humidity. Curves are included for the theoretical increase of water content with longitudinal tensile stress over the whole range of humidity, and for the theoretical decrease in water content under lateral compressive stress. The latter effect may be as much as 200 times the former, on account of the anisotropy of swelling.