It is the merit of Jacques Loeb to have shown us the necessity of simplifying our methods of attacking biologic problems. Instead of investigating the effects of complex substances on still more complex living organisms, he took up the simplest things imaginable, the familiar inorganic salts, and for his living subject the least complex complete organism possible—the single cell, sans blood, sans nerves, sans soul, sans everything. We pathologists cannot so readily reduce our subjects of investigation to such simple terms, but are forced too often, by the nature of our problems, to the opposite extreme, with such unsatisfactory results as might be expected. The situation of a pathologist, trying to investigate the action of a bacterial toxin of absolutely unknown composition on the equally unknown compounds of a complex mammalian organism, reminds us pathetically of the grotesque figure in "Confessio Medici," of the blind man searching in a dark room