Remak, Robert (1815–1865), German neurologist and embryologist. Remak published his first studies on the fine structure of nerve tissue in 1836 and published his dissertation on the subject two years later. He studied the function of the sympathetic nervous system, coming to the conclusion that the function of these nerves was concerned with all involuntary muscle movement, with secretion, and possibly with the skin. In 1843 and 1844 he demonstrated the presence of extremely thin fibrils in the axis cylinder, the central core of nerve fibers. As an embryologist Remak conducted research on chicken embryos. In 1842 he discovered the three germ layers of the embryo: the ectoderm, the mesoderm, and the endoderm.