In my article Wing-Beats, which appeared in this Journal, in the issue of October, 1930, I recorded a series of experiments demonstrating the strength and lightness of a spring formed by twisting skeins of natural silk.

My hope is that silk torses of this kind will fulfil, in human flight, the postural function of a bird's pectoral muscles, leaving to human effort the phasic function of these muscles, that is to say, the activity induced by rapid nerve impulses from the brain.

The ratio that may subsist between these two functions cannot, I think, be determined otherwise than by full-scale flight experiments, but the experiments already recorded give reasonable ground for the belief that the requisite human phasic output will be small in relation to the total weight movement.