Marie-François-Xavier Bichat and the Tissue Doctrine of General Anatomy
Marie-François-Xavier Bichat and the Tissue Doctrine of General Anatomy
Long before the development of cell theory, philosophers and anatomists speculated about the nature of constituents of the human body that might exist below the level of ordinary vision. Even after the introduction of the microscope in the seventeenth century, however, investigators still argued about the level of resolution that might be applicable to studies of the human body. By the eighteenth century, many anatomists had abandoned humoral pathology and, in analyzing the structure and function of organs and organ systems, hoped to discover correlations between localized lesions and the process of disease. Tissue doctrine was elaborated by the great French anatomist Marie-François-Xavier Bichat (1771-1802) as an answer to the question about the constituents of the body. As a result of Bichat's ingenious approach to the study of the construction of the body, he is considered the founder of modern histology and tissue pathology. His pioneering work in anatomy and histology has been of lasting value to biomedical science. Bichat's approach involved studying the body in terms of organs, which were then dissected and analyzed into their fundamental structural and vital elements, called "tissues." This attempt to create a new system for understanding the structure of the body culminated in the tissue doctrine of general anatomy.
As the son of a respected doctor, Bichat was expected to enter the same profession. After studying medicine at Montpellier, Bichat continued his surgical training at the Hôtel Dieu in Lyons. The turmoil caused by the French Revolution, however, forced him to leave the city for service in the army. In 1793 he was able to resume his studies in Paris and became a student of the eminent surgeon and anatomist Pierre-Joseph Desault (1744-95). In 1800 Bichat became physician at the Hôtel Dieu. One year later, he was appointed professor. Completely dedicated to anatomical and pathological research, Bichat essentially lived in the anatomical theater and dissection rooms of the Hôtel Dieu, where he performed at least 600 autopsies in one year. In 1802 he became ill with a fever and, barely 31 years of age, died before completing his last anatomical treatise.
Working in the autopsy rooms and wards of the hospitals of Paris, Bichat and his colleagues were committed to the goal of transforming the art of medicine into a true science. Bichat believed this goal could only occur when physicians adopted the method of philosophical analysis used in the other natural sciences. Research on the fundamental structure of the body would transform observations of complex phenomena into precise and distinct categories. This approach and the movement to link postmortem observations with clinical studies of disease were largely inspired by the work of the great French physician Philippe Pinel (1755-1826). Honored for his Philosophical Nosography (1798), Pinel argued that diseases must be understood not by references to humoral pathology but by tracing them back to the organic lesions that were their sources. Because organs were composed of different elements, research, in turn, must be directed towards revealing the fundamental constituents of organs.
Bichat reasoned that organs that manifested analogous traits in health or disease must share some common structural or functional components. Failing to find this analogy at the organ level, he conceived the idea that there might be some such analogy at a deeper level. His approach involved studying the body in terms of organs that could be broken down into their fundamental structural and vital elements, which he called "tissues." Organs had to be teased apart by dissection, maceration, cooking, drying, and exposure to chemical agents such as acids, alkalis, and alcohol. According to Bichat, the human body could be resolved into 21 different kinds of tissue, such as the nervous, vascular, connective, bone, fibrous, and cellular tissues. Organs, which were made up of assemblages of tissues, were, in turn, components of more complex entities known as organ systems.
Tissues were units of function as well as structure. The actions of tissues were explained in terms of irritability (the ability to react to stimuli), sensibility (the ability to perceive stimuli), and sympathy (the mutual effect parts of the body exert on each other in sickness and health). Obviously, Bichat's "simple" tissues were themselves complex; they were just simpler than organs, organ systems, or the body as a whole. Tissues, as Bichat himself acknowledged, consisted of combinations of interlaced vessels and fibers. Thus, Bichat's tissue theory of general anatomy provided no actual unit of basic structure that could not be further subdivided. Thus, Bichat's concept of the tissue is not like the concepts now associated with the cell or the atom. Nevertheless, Bichat hoped that his analysis of the structure of the human body would lead to a better understanding of the specific lesions of disease and improvements in therapeutic methods.
Embryology was essentially outside the boundaries of Bichat's own research program, and his account of the arrangement of animal tissues generally ignored the problem of tracing the origins of specific organs and tissues back through their embryological development. Bichat's goals and guiding principles were thus different from those that motivated the founders of cell theory. In formulating his doctrine, Bichat's objective was not merely to extend the knowledge of descriptive anatomy but to provide a scientific language with which to describe pathological changes. Through an understanding of the specific sites of disease, he expected better therapeutic methods eventually to emerge.
Bichat's dedicated disciples studied his writings and arranged to have them translated into other languages. In Treatise on Tissues (1800), Bichat presented his objectives for a new science of anatomy and pathology. In essence, he believed that an accurate classification of the different tissues of the body was fundamental to the new science. An anatomist would have to know the distribution of tissues in the various organs and parts of the body and the susceptibilities of specific tissues to disease. These themes were developed further in his General Anatomy, Applied to Physiology and Medicine, a work which has been called one of the most important books in the history of medicine. Bichat's last great work, the five-volume Treatise of Descriptive Anatomy, was unfinished at the time of his death.
Clearly, Bichat's tissue theory of general anatomy is quite different from the cell theory that was elaborated in the nineteenth century by Matthias Jacob Schleiden (1804-1881) and Theodor Schwann (1810-1882). Cell theory is a fundamental aspect of modern biology and implicit in our concepts of the structure of the body, the mechanism of inheritance, development and differentiation, and evolutionary theory.
Many of Bichat's followers came to regard the tissue as the body's ultimate level of resolution. Among the more conservative French physicians—even after cell theory had been well established for both plants and animals—the tissue was still considered the natural unit of structure and function. Many agreed with Bichat's well-known skepticism concerning microscopic observations. The microscope was not a trustworthy tool for exploring the structure of the body, Bichat cautioned, because every person using it saw a different vision. Many microscopists had reported that biological materials were composed of various sorts of globules. While some of these entities might have been cells, in many cases they were probably just optical illusions or artifacts. Although Bichat's work is often regarded as the foundation for the science of histology, the word "histology" was actually coined about 20 years after his death.
LOIS N. MAGNER
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