Bichat, Marie François Xavier (ma REE fran SWAH gzah VYAY bee SHAH) (1771-1802) a French surgeon, was the first scientist to base anatomy and physiology on the study of tissues, rather than organs. One of the founders of histology, the study of animal and plant tissues, he also advocated the use of autopsy to study disease.

Bichat, like his father before him, studied medicine, although military service during the French Revolution interrupted his education. In the mid-1790's, he became a professor of medicine in Paris. Bichat's insight that the body's diverse organs consist of different tissues led him to classify tissues into three types of membranes—fibrous, mucous, and serous—and to describe 21 distinct types of tissues.

Bichat performed over 600 autopsies, during which he examined how disease affected organs. These examinations led to his realization that pathology should be based on the study of the affected tissues of the organ rather than on the organ itself.

Although Bichat helped found histology, the study of tissues, he was wary of the microscope and hardly used it. Nonetheless, his work provided a basic structure for studying anatomy and physiology by demonstrating that organs' complex structures could be understood in terms of their elementary tissues.

Bichat was also a philosopher who believed that life could not be understood in terms of physical laws alone. In his Physiological Researches on Life and Death (1800), he defined life as “the sum total of forces that resist death.” His other books include General Anatomy, Applied to Physiology and Medicine (1801).