IN A PRECEDING paper 1 data relating to the chemical evidences of respiratory insufficiency in acute poliomyelitis, with early respiratory muscle paralysis, have been presented. It was shown that oxygen lack and carbon dioxide retention did not occur until after respiratory muscle paralysis had become extensive and the clinical evidence of dyspnea was clearly evident. In fact, it was shown that in most patients with early and partial respiratory muscle paralysis actual hyperpnea occurred in spite of this handicap. As discussed in the previous paper, there has been some concern that early use of the respirator may increase the ultimate dependence of a patient upon respiratory aid and aggravate the tendency for the development of psychogenic hyperpnea and addiction to the respirator. The reasons for considering that early respiratory aid may be advisable are based on the general principle of the benefit of rest in the invasion stage of acute