ter to its stimulating effects until, eventually, the center no longer responds to the presence of carbon dioxide. Thus, in chronic emphysema, the respiratory center-rather than responding to carbon dioxide concentrations-is stimulated by the chemoreceptors which respond to low oxygen tensions of the blood. In other words, the sole respiratory stimulant is hypoxia. If this stimulus is removed by intensive oxygen therapy, the respiratory center has no stimulation and therefore ceases to function. Careless administration of high r to its timulating effects until, entually, the c nt r no longer reconcentrations of oxygen can throw the patient into complete respiratory failure. This can be prevented if the oxygen administration is started slowly so that the respiratory center is allowed time to regain some of its normal sensitivity to lowered carbon dioxide levels. The oxygen is then increased gradually to the desired