Prolonged exposure of a limb to cold water causes the disease known as immersion foot. The widespread literature has been reviewed elsewhere (1). Neuromuscular dysfunction and histopathological changes in nerve, muscle, and other tissues are readily demonstrated after such exposure. The question of how cold short of freezing damages the tissues has not been settled. Goldschmidt and Light (2) and Lewis and Love (3) suggested that the poor dissociation of oxygen from cold hemoglobin may make the tissues anoxic. It is true that the supply of oxygen by cold hemoglobin is meager (4) but it is also true that the utilization of oxygen by tissues is conspicuously lowered at such reduced temperature (5). We have demonstrated in short term experiments a reduced oxygen tension of the skin of man exposed to cold (6). The present experiments were carried out in order to learn to what extent, if any, prolonged exposure to cold lowers the oxygen tension of muscle and of the subcutaneous space, and whether oxygen inhalation will increase the oxygen tensions. Preliminary experiments on the effect of cold on the skin of human extremities were abandoned because of the danger involved. Rabbits were chosen because there has been some experience in producing immersion foot in that animal (7). Parallel studies were made of the temperatures of the muscle and of the subcutaneous tissue in order to learn the degree of chilling of tissues and in order to get some idea of the rate of blood flow through the tissues during prolonged chilling. METHODThe open tip platinum electrode (8) for estimating oxygen tension was utilized as previously described (6) except for several modifications. The electrode consists of the sharpened tip of a 0.2 mm. platinum wire, the rest of the wire electrically insulated. At voltage 0.6V. the current measured is linearly proportional to the rate of diffusion of oxygen to the electrode. For greater sensitivity to lower oxygen tension in these studies, electronic amplification was substituted for the galvanometer used in previous studies. The circuit was a modification of that used by Moody for ionization chamjer work (9).The electrodes and their wire connections were insulated to minimize electrical leakage in the special condition of underwater work. In spite of this, electrical leakage was not abolished in all experiments. When it occurred the data had to be discarded as were data from an occasional unresponsive electrode. The electrodes were placed in subcutaneous areas rather than in skin because rabbit skin is so thin as perhaps to allow its oxygen tension to be influenced by oxygen of the surrounding water and of the subcutaneous space. All data were corrected for direct temperature effect on electrical current as previously found for these electrodes (6). Measurements were made without calibrating (6) the electrodes, and the data are presented as relative (Figure 3) since the absolute values of oxygen tension are not known. We were especially interested in the changes in oxygen tension in muscle becaus...

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