Quinine is, above all, a protoplasmic poison, devitalizing the blood and tissues ; it particularly retards the elimination of nitrogenous waste (urea and uric acid), and causes the retention and accumulation of effete products in the system (though for a time the diminished waste gives a sense of "tone" to the system, the ultimate result is deplorable). It causes congestion of the brain, and, in large doses, abolishes the cerebral functions. It is an irritant to serous membranes and to the skin ; it causes deafness and serous inflammation of the internal ear ; blindness, ischaemia of the retina and optic neuritis ; it produces stupor, delirium and even convulsions. (Epilepsy is intensely aggravated by it.) Quinine, however, arrests the development of low forms of vegetable life, and especially of the poison of marsh malaria, but it rarely antidotes the effects of the poison on the system.