Retinitis pigmentosa is a manifestation of a widely branching complex, the nucleus of which lies in the pathologically altered hormonal functions of the pituitary and diencephalon. There are 2 great classes of the disease. The 1st is the hereditary type, dominant or recessive, and this is primarily a neuro-cellular disease of certain areas of the brain and retina. The 2d is the "sui generis" autonomous type. These latter cases are often unilateral. They may follow vaccination, typhus, the exanthemata, persistent vascular spasm, etc., and it is presumed that in each case the toxins, etc., of the disease also upset the secretory balance of the pituitary, producing a hormonal dysfunction. The transplantation of such "biogenic stimulators" as placenta into the subconjunctival tissues according to the method of Filatov may help in these latter cases but it can be of no value in the hereditary type.