In order to pursue chemotherapy successfully we must look for substances which possess a high affinity and high lethal potency in relation to the parasites, but have a low toxicity in relation to the body, so that it becomes possible to kill the parasites without damaging the body to any great extent. We want to hit the parasites as selectively as possible. In other words, we must learn to aim and to aim in a chemical sense. The way to do this is to synthesize by chemical means as many derivatives as possible of relevant substances.

It has been shown to be possible, by deliberately planned and chemotherapeutic approach, to discover curative agents which act specifically and aetiologically against diseases due to protozoal infections, and especially against the spirilloses, and amongst these against syphilis in the first place. Further evidence for the specificity of the action of dihydroxydiaminoarsenobenzene [Salvarsan '606'] is the disappearance of the Wasserman reaction, which reaction must ... be regarded as indicative of a reaction of the organism to the constituents of the spirochaetes.

Success in research needs four Gs: Glück, Geduld, Geschick und Geld. Luck, patience, skill and money.

The history of the knowledge of the phenomena of life and of the organized world can be divided into two main periods. For a long time anatomy, and particularly the anatomy of the human body, was the a and ? of scientific knowledge. Further progress only became possible with the discovery of the microscope. A long time had yet to pass until through Schwann the cell was established as the final biological unit. It would mean bringing coals to Newcastle were I to describe here the immeasurable progress which biology in all its branches owes to the introduction of this concept of the cell. For this concept is the axis around which the whole of the modem science of life revolves.

The organism possesses certain contrivances by means of which the immunity reaction, so easily produced by all kinds of cells, is prevented from acting against the organism's own elements and so giving rise to auto toxins ... so that one might be justified in speaking of a 'horror autotoxicus' of the organism. These contrivances are naturally of the highest importance for the existence of the individual.

We may regard the cell quite apart from its familiar morphological aspects, and contemplate its constitution from the purely chemical standpoint. We are obliged to adopt the view, that the protoplasm is equipped with certain atomic groups, whose function especially consists in fixing to themselves food-stuffs, of importance to the cell-life. Adopting the nomenclature of organic chemistry, these groups may be designated side-chains. We may assume that the protoplasm consists of a special executive centre (Leistungs-centrum) in connection with which are nutritive side-chains... The relationship of the corresponding groups, i.e., those of the food-stuff, and those of the cell, must be specific. They must be adapted to one another, as, e.g., male and female screw (Pasteur), or as lock and key (E. Fischer).