1. Concepts on the Causal Genesis of Human Intestinal Tumors The action of chemical substances has a significant role in the genesis of human tumors. It is assumed that most human tumors are induced by exogenous chemical noxae (Schmahl, 1970;Heidelberger, 1975; and others). In the course of intensive efforts to discover the principles of tumor etiology, important insights have resulted in recent years. These are that chemical carcinogens do not only arise as products of our tech nological civilization, but that they also occur in nature as potent solitary carcinogens and cocarcinogens (e. g., as plant products). For review, see Hecker (1972) and Preuss mann (1975). Not only "complete" carcinogens are significant for the genesis of tu mors, but also substances which are first transformed to the actual carcinogenic com pound in the organism (Schmahl, 1975). The causal significance of exogenous noxae in carcinogenesis is indicated by the fact emphasized by Bauer (1963) that malignant tumors occur predilectively at those sites in the body which are in direct or indirect contact with the environment. This applies especially to the intestinal tract."

This is a reproduction of a book published before 1923. This book may have occasional imperfections such as missing or blurred pages, poor pictures, errant marks, etc. that were either part of the original artifact, or were introduced by the scanning process. We believe this work is culturally important, and despite the imperfections, have elected to bring it back into print as part of our continuing commitment to the preservation of printed works worldwide. We appreciate your understanding of the imperfections in the preservation process, and hope you enjoy this valuable book. ]+++ The below data was compiled from various identification fields in the bibliographic record of this title. This data is provided as an additional tool in helping to ensure edition identification: ++++ Anweisung Zum Anbau Des Nadelholzes Dietrich E. Kunze Helwing, 1788