This classic work showed that Müller realized the necessity of the cell theory for the comprehension of the nature of cancer. He recognized cells, their nuclei and nucleoli, and could distinguish various types of tumors microscopically. Only Lieferung 1 of the book was published; C. West translated it into English in 1840. Improved translation with important commentary in L.J. Rather, P. Rather, & J.B. Frerichs, Johannes Müller and the nineteenth-century origins of tumor cell theory, Canton, Mass, Science History Publications, [1986].