As biologists have learned to see species as historical creations, not embodiments of some essential reality, so too must historians learn to think of disciplines as human creations, not subdivisions of a fixed natural order. The scope and thrust of biochemistry were, at crucial points in its history, very much up for grabs; at all times, they were subject to some degree of local interpretation. One must think of biochemistry in two complementary ways: as a body of work in the biomedical aspects of chemistry and as a political or institutional rubric that varies with time and locale. I use the term “biochemistry” to refer to the timeless extended family of biochemistries; when referring to specific historical groups, I use the terms they themselves used: physiological or pathological chemistry, medical chemistry, biological chemistry, and biochemistry, because that term too identifies a group of historical actors. “Biochemistry” has two meanings here, which is awkward, but inescapable.

Most academic disciplines originated in the rather brief period of active institution building in Germany, from 1840 to 1890. In physiological chemistry, as in most fields of science, Germany took a strong and early lead. Yet physiological chemistry was an anomaly; it was not a story of rapid and successful specialization and growth. Germans led in the production of biochemical research; but there were few institutions of physiological chemistry and these had little growth potential.

Histories of the scientific disciplines are not new, but in recent years historians of science have begun to write them in a new way. Older histories were often written by scientists turned historians and were insiders' accounts of the accumulation of more perfect knowledge. They did not inquire why the world of knowledge is divided up as it is, or how it got that way, any more than naturalists before Darwin's generation worried about the origin and extinction of species. There was no particular reason for scientist historians to see how their disciplines were shaped by processes of social and economic adaptation and competition. Disciplines were the framework for descriptive natural histories of knowledge, not for analyses of the evolution and perpetuation of social forms.

Disciplines are political institutions that demarcate areas of academic territory, allocate the privileges and responsibilities of expertise, and structure claims on resources. They are the infrastructure of science, embodied in university departments, professional societies, and informal market relationships between the producers and consumers of knowledge. They are creatures of history and reflect human habits and preferences, not a fixed order of nature. There have as yet been few studies of sciences as institutions, and it is this aspect of the discipline of biochemistry that will concern me here. I will have less to say about biochemistry as a system of ideas than about biochemists' collective efforts to build and maintain their own institutions.

The influence of chemistry in biochemistry may seem as amorphous and boundless a theme as the influence of theology in the church. At the beginning, nearly a third of the members of the American Society of Biological Chemists had Ph.D. degrees in chemistry. Half of ASBC members who got their degrees between 1900 and 1910 joined the American Chemical Society; no fewer than 85% of the cohort with doctorates between 1930 and 1934 did so. It is rare to find biochemists who did not take their undergraduate work in chemistry. Most chemists regarded biochemistry as an applied branch of their discipline, and their views enjoyed increasing deference from biochemists. How, then, to dissect such a close-woven tissue of relationships? As in the preceding chapter, we must concentrate on institutionalized roles and channels of influence. We must see what systematic opportunities there were for recruitment of chemists or for cooperative relations. We must see how adoption of chemists' theories and methods conferred strategic advantages for discipline building. We must understand how chemists' disciplinary ambitions and their role in medical school departments shaped the practice of biochemistry.

The language of “hybrid” disciplines should not mislead us into assuming that chemistry and biology or medicine had equal or symmetrical roles in the genesis and nurture of biochemistry. In fact, they did not. Biology and medicine provided problems; chemistry provided means. (Chemical means did tend, of course, to become biochemical ends.) Few biochemists came from backgrounds in biology or the biomedical sciences; chemistry was the principal source of recruits.

The reorganization of medical institutions created opportunities for growth and innovation in all the preclinical disciplines. Because the reform movement emphasized intellectual quality and uniform standards, competition for regional or national leadership became a powerful argument for higher budgets. Discipline builders were liberated from local medical politics. Workers in all disciplines were encouraged to acquire specialized academic credentials and to engage in fashionable lines of research. Each discipline adapted these new resources to its particular needs, but the basic strategies are similar in all.

As universities gained control of the preclinical sciences, they established academic criteria for appointments and promotion. The AMA Council on Education in 1909 was unanimous and vehement in their opinion that physiology and biochemistry should be taught by full-time specialists: “The old but still prevalent idea that almost any young practitioner with time on his hands could do as professor of physiology cannot be too forcibly condemned.”

More sophisticated medical students made it possible for anatomists, physiologists, and biochemists to teach more specialized courses and to teach them as basic experimental sciences. The new professionals had much higher expectations than the pioneers. For example, Henry Pickering Bowditch had had to bootleg laboratory instruction into his lectures on medical physiology; his disciple, William T. Porter, saw lectures and medical application as incidental to pure experimental physiology. Here is the difference between the generations: what had been academic frosting for the pioneers was cake for the new professionals. Research achievement became as important as teaching skills in building the reputation of a school.

Particular scientific styles flourish only where intellectual priorities are congruent with institutional structures and goals. That is the central theme of Chapters 9–11. This process of accommodation is clearest in the case of clinical biochemistry. True, the time was ripe for discoveries in clinical analysis, metabolism, and nutrition; but biochemists' concentration on these problems reflects an institutionalized system of service roles, markets, and professional alliances. Because human and material resources were readily mobilized for clinical biochemistry, this style dominated the discipline for a generation or more. Meanwhile, equally attractive opportunities for discovery in chemical biology did not become fashionable, except in a few marginal contexts where intellectual opportunities were also vehicles for marshaling institutional support. Contexts that provided intellectual support for chemical biology generally also had built-in limits to growth. This was the case in most departments of chemistry and biology and in nonmedical programs of general physiology. Because bioorganic chemistry or chemical biology conferred little strategic or political advantage, these programs did not attract large numbers of biochemists.

This argument assumes a stringent process of selection: intellectual styles that do not fit institutional goals will not survive. This may be a realistic assumption for periods of rapid institutional innovation. Institution builders must be aware of the strategic uses and limitations of disciplinary programs; entrepreneurs must accommodate their ideals to market conditions. Once established, however, institutions are neither fixed nor inflexible; fixed structures can usually be adapted to a wide variety of uses.

In Britain biochemistry developed within departments of physiology, beginning as a specialized subfield, chemical physiology, and gradually achieving independent status as a separate discipline. This was the prevalent German pattern; alternative German modes were virtually absent. There were regional differences, but what is striking is the consistency of British biochemical institutions (see Table 3.1). Lectureships, or assistant professorships, in chemical physiology were first established in the leading medical schools during the period from 1895–1905; the smaller provincial universities of the midlands followed suit from 1909 to 1914, and the larger technological universities in the 1920s.

There were a few exceptions: at Bristol University and Imperial College, biochemistry was attached to chemistry and botany. Chemist Chaim Weizmann was a lecturer and then a reader in biochemistry (really fermentation chemistry) in William Perkins's department of chemistry at Manchester from 1910 to 1915. The most important exception was Liverpool University, where the first chair of biochemistry was established in the School of Public Health. But within a decade it too had reverted to the norm, a chair of chemical physiology. Roles for biochemists were established in a few London hospitals; R. H. A. Plimmer and John A. Gardner taught biochemistry at St. Thomas's and St. George's before World War I. E. C. Dodds made the Courtauld Institute of Pathology at Middlesex Hospital into a leading center of clinical biochemistry in the 1920s. But these were marginal to the mainstream of the discipline.

Because Germany was so advanced in developing scientific disciplines, German influence was inevitably a major force in the development of the biomedical sciences in Austria, Russia, Japan, Scandinavia, and the United States. Some German laboratories had more foreign than German students. Walter Jones's description of the polyglot character of Kossel's institute at Marburg is typical:

Some universities organized special courses in English, and foreign students were regarded as an important vehicle of German cultural imperialism.

Apart from Russia, the United States was probably the most avid consumer of German Wissenschaft. It has been estimated that about 15,000 American doctors studied in German (or Austrian) universities prior to 1914, or about one-third of the upper elite of American physicians. The importance of German contacts in agricultural chemistry and in the establishment of American agricultural experiment stations has also been documented.

In June 1847 William Thomson, later Lord Kelvin (1824–1907), met Joule at the Oxford meeting of the British Association for the Advancement of Science, and the encounter led Thomson to study Joule's papers on the mutual convertibility of heat and mechanical work. At the Oxford meeting Joule had read a paper describing his measurement of the temperature change in a fluid agitated by a paddle wheel that was turned by a descending hanging weight; he claimed to have determined the quantitative equivalence between the heat generated by the paddle wheel and the mechanical work required to generate that heat. Thomson found Joule's conclusions astonishing; and he reported Joule's work to his brother James Thomson (1822–92), who confessed that Joule's ‘Views have a slight tendency to unsettle one's mind’. The Thomsons' sense of intellectual disorientation arose from their belief, derived from the work of Sadi Carnot (1796–1832), that heat was conserved in the generation of mechanical work by heat engines. This theory seemed to contradict Joule's claim that heat must be consumed in the generation of work. The unravelling of the apparent contradiction between the theories of Carnot and Joule was to lead to the formulation of the science that in 1854 William Thomson was to term ‘thermo-dynamics’, the theory of the mechanical action of heat.

In his 1900 lecture ‘Nineteenth century clouds over the dynamical theory of heat and light’, William Thomson pointed to two problems facing the mechanical theory of nature: the failure to explain the mechanism of the motion of the earth through the ether, and the difficulty the concept of the equipartition of energy posed for the construction of molecular models. Thomson highlighted two ‘clouds’ that threatened his elaboration of mechanical models of physical phenomena, but there were wider dimensions to the difficulties that physicists perceived in the conceptual rationale of the mechanical theory of nature.

The traditional programme of mechanical explanation elicited diverse responses from physicists in the 1880s and 1890s. Thomson's ether models and Boltzmann's lectures on field theory continued the programme of elaborating detailed mechanical models of phenomena. Boltzmann strove to provide an exhaustive treatment of every detail of the structure and motions of his mechanical models of the electromagnetic field; and Thomson declared that the construction of a mechanical model of a phenomenon was the criterion of the intelligibility of that phenomenon. Nevertheless, the conceptual difficulties associated with the enunciation of mechanical models were well understood. Maxwell had pointed out that such models could not provide unique explanations of phenomena and had drawn attention to the dangers of confusing representation and reality, and though he remained committed to the ultimate aim of formulating a ‘complete’ mechanical theory of the field, in his Treatise he employed an analytical formulation of dynamics, rather than a specific mechanical model.

The physical constitution of matter appeared uncertain in the nineteenth century. Although an ontology of particles of matter in motion was fundamental to the programme of mechanical explanation and to the conceptual coherence of the science of thermodynamics, physicists were careful to distinguish between the general supposition of a particulate theory of matter and the adoption of more specific models of molecular structure. Though the mechanical view of heat as the motion of the particles of matter underlay the principle of the equivalence of heat and work, physicists found compelling evidence for a molecular theory of matter only with the development of the kinetic theory of gases in the 1850s. But the problem of explaining the phenomena of spectroscopy indicated the need to suppose complex internal molecular vibrations, and raised difficult questions about the formal coherence of the kinetic theory of gases. The problems of molecular physics raised crucial issues about the conflicting empirical constraints (from spectroscopy and the kinetic theory of gases) on the formulation of a coherent theory of the molecular structure of bodies. The problems of molecular physics shaped the development of thermodynamics: The statistical theory of molecular motions, which was formulated as a seminal feature of the kinetic theory of gases, led to the interpretation of the second law of thermodynamics as an irreducibly statistical law. For chemists, the problems of matter theory seemed equally complex, and the status of the atomic theory remained the subject of debate.

In the nineteenth century the term ‘physics’ acquired new and significant connotations. Although the term was still occasionally used in the traditional sense to refer to natural science in general, by the early nineteenth century ‘physics’ was being used in the modern and more specialised sense to denote the study of mechanics, electricity, and optics, employing a mathematical and experimental methodology. In the article entitled ‘Physical Sciences’ in the ninth edition of the Encyclopaedia Britannica in the 1870s, James Clerk Maxwell identified the scope of physics with the programme of mechanical explanation, first enunciated in the seventeenth-century ‘mechanisation of the world picture’, which sought to explain physical phenomena in terms of the structure and laws of motion of a mechanical system. In a critical exposition of current physical theory, The concepts and theories of modern physics (1881), Johann Bernhard Stallo gave an informative and more detailed definition of the theoretical structure of physics as conceived by contemporary theorists:

The science of physics, in addition to the general laws of dynamics and their application to the interaction of solid, liquid and gaseous bodies, embraces the theory of those agents which were formerly designated as imponderables – light, heat, electricity and magnetism, etc.; and all these are now treated as forms of motion, as different manifestations of the same fundamental energy.

In the nineteenth century the science of physics came to be defined in terms of the unifying role of the concept of energy and the programme of mechanical explanation.

The period circa 1800–1900 corresponds to a distinctive phase in the conceptual development of physics, bounded by the increasing dominance, from the late eighteenth century on, of quantification and the search for mathematical laws, together with the emergence of a unified physics based on the programme of mechanical explanation, and by the development in the early twentieth century of the quantum and relativity theories. I have aimed to provide a study of the development of physics in the nineteenth century in a form accessible to the reader without a specialised knowledge of physics and mathematics. The argument of the book is structured around the major conceptual problems of nineteenth-century physics: the emergence of energy physics and thermodynamics, the theory of the luminiferous and electromagnetic ether and the concept of the physical field, molecular physics and statistical thermodynamics, and the dominance of the programme of mechanical explanation. The book begins with an account of the transformation in the scope of the science of physics in the first half of the nineteenth century.

I am grateful to John Heilbron for reading a portion of the manuscript and to Crosbie Smith for reading the whole manuscript of this book, and for their helpful comments. I am also grateful to the Syndics of the Cambridge University Library for their kind permission to reproduce documents in their keeping, and to the Council of the Royal Society for the award of a grant for research undertaken in the preparation of this book.