IT is now well established that hydrogen bonding takes a major role in the stabilization of wool keratin. This is well demonstrated by the recent finding1 that wool fibres supercontract by 70 per cent of their length in 1 N hydrochloric acid containing 4 M concentrations of sodium iodide. In agreement with earlier workers2, it was considered that the process took place in two phases corresponding to areas of strong and weak hydrogen bonding lying in series along the microfibrils.