Today, the concept of specific receptors for drugs and transmitters lies at the very heart of pharmacology. Less than one hundred years ago, this novel idea met with considerable resistance in the scientific community. To mark the 150th anniversary of the birth of John Newport Langley, one of the founders of the receptor concept, we highlight his most important observations, and those of Paul Ehrlich and Alfred Joseph Clark, who similarly helped to establish the receptor theory of drug action.

The concept of specific receptors that bind drugs or transmitter substances onto the cell, thereby either initiating biological effects or inhibiting cellular functions, is today a cornerstone of pharmacological research and pharmaceutical development. Yet, while the basic ideas of this concept were first explicitly formulated in 1905 by the Cambridge physiologist John Newport Langley (1852–1925), drug receptors remained hypothetical entities at least until the end of the 1960s. Without doubt, the development of receptor-subtype specific pharmaceuticals—especially the beta-adrenergic receptor antagonist propranolol (introduced in 1965)—promoted the acceptance of the receptor concept in pharmacology. It was only in the 1970s, however, that receptors began to be isolated as specific proteins of the cell membrane and that their composition and conformation began to be explored. During the last twenty years the modern techniques of molecular biology have helped to determine the genetic basis of receptor proteins, to identify their amino acid sequences, and to further elucidate their remarkable structural diversity as well as their similarities and evolutionary relationships. Numerous receptor types and subtypes have since been characterized.

This paper elucidates the origins of scientific work on stem cells. From the late nineteenth century onwards, the notion of stem cells became customary in scientific communities of Imperial Germany. Adopting the term Stammzelle from Ernst Haeckel, Theodor Boveri was influential in introducing the concept in embryological studies and early genetics around 1900, describing a capacity of stem cells for self-renewal as well as differentiation. At the same time, blood stem cells were conceptualized by histologists such as Ernst Neumann and Artur Pappenheim in studies of physiological haematopoiesis and various forms of leukaemia. Furthermore, building on Julius Cohnheim's theory that tumours arise from ‘embryonic remnants’ in the adult body, pathologists aimed at identifying the cells of origin, particularly in the embryo-like teratomas. Embryonic stem cells thus assumed an ambiguous status, partly representing common heritage and normal development, and partly being seen as potential causes of cancer if they had been left behind or displaced during ontogeny. In the 1950s and 1960s experimental research on teratocarcinomas by Leroy Stevens and Barry Pierce in the USA brought together the strands of embryological and pathological work. Alongside the work of Ernest McCulloch and James Till at the Ontario Cancer Institute from the early 1960s on stem cells in haematopoiesis, this led into the beginnings of modern stem cell research.

In present-day pharmacology and medicine, it is usually taken for granted that cells contain a host of highly specific receptors. These are defined as proteins on or within the cell that bind with specificity to particular drugs, chemical messenger substances or hormones and mediate their effects on the body. However, it is only relatively recently that the notion of drug-specific receptors has become widely accepted, with considerable doubts being expressed about their existence as late as the 1960s. When did the receptor concept emerge, how did it evolve and why did it take so long to become established?

The Berlin physician Albert Moll (1862-1939) was an advocate of hypnotic suggestion therapy and a prolific contributor to the medical, legal and public discussions on hypnotism from the 1880s to the 1920s. While his work in other areas, such as sexology, medical ethics and parapsychology, has recently attracted scholarly attention, this paper for the first time comprehensively examines Moll's numerous publications on hypnotism and places them in their contemporary context. It covers controversies over the therapeutic application of hypnosis, the reception of Moll's monograph Der Hypnotismus (1889), his research on the rapport between hypnotizer and subject, his role as an expert on 'hypnotic crime', and his views on the historical influence of hypnotism on the development of psychotherapy. My findings suggest that Moll rose to prominence due to the strong late-nineteenth-century public and medical interest in the phenomena of hypnosis, but that his work was soon overshadowed by new, non-hypnotic psychotherapeutic approaches, particularly Freud's psychoanalysis.