The state of water in muscle and blood and the osmotic behaviour of muscle

In the course of the investigation described in the preceding paper by Hill and Kupalov it became necessary to determine the amount of “free” water in muscle, i.e., the weight of water per gramme of muscle which is capable of dissolving in a normal manner (with the normal depression of vapour pressure) substances added to it. For many years, chiefly on the evidence of the experiments of Overton (1902), it has been commonly supposed that a large proportion of the water of muscle exists in some “bound” form, incapable of taking part in the osmotic changes which occur when the tissue is immersed in hypoor hyper-tonic solutions. From the fact that a muscle swells to much less than twice its initial weight when immersed in a solution of half the initial osmotic pressure Overton concluded “dass nicht das gesammte im Muskel befindliche Wasser in der Form eines Lösungsmittels enthalten sein kann.” I have confirmed Overton’s experiments (see below) but believe that a very different explanation of them is necessary.