Engelmann (5) showed that the cells of the ciliated epithelium of the frog’s œsophagus remain active for as much as two hours after the tissue is exposed to an atmosphere of hydrogen. From this he concluded that the cells contained a considerable store of intramolecular oxygen, on which they could draw in the total absence of atmospheric oxygen. This experiment is, however, not conclusive. In the case of the cilia on the gills of
Mytilus edulis
, the absolute time required for cessation of movement in hydrogen depends very largely on the amount of water in contact with the tissue. Oxygen dissolved in an undisturbed drop of water is only slowly removed by a current of hydrogen; in a large drop of water there is, therefore, more oxygen available for the use of the tissue than is the case when the experiment is performed with tissue simply moistened with water. If a piece of gill, kept moist but not immersed in sea-water, is placed on a coverslip in an Engelmann gas chamber and exposed to an atmosphere of hydrogen, active movement persists for 30 to 45 minutes; the speed of the beat gradually falls, and after 60 to 75 minutes all movement ceases. If air be admitted when the movement has begun to slow down partial recovery takes place at once, and is soon complete. If, however, the cilia have become almost inactive in hydrogen, recovery in air is much slower, and may not be complete for about half an hour. In pure oxygen recovery is much more rapid. In order to determine to what extent the prolonged activity of the cells in an atmosphere of hydrogen is due to free oxygen in the water or tissue, the experiments were repeated with hæmoglobin in sea-water. A solution of hæmoglobin was used of such a strength as would enable a film of liquid in contact with the tissue to give a well-marked spectrum with a Zeiss microspectroscope. The following table gives the details of a typical experiment.
Metal hydride hydrogen storage and purification technologies
