Transcriber's Note: Minor typographical errors and inconsistencies have been corrected. Some words had inconsistent hyphenation throughout the book; these have been made consistent. In the mathematical and chemical expressions, the caret character represents "to the power of", e.g. e^2 means e-squared. Curly braces are used to represent underscores, e.g. n{1} means n with a subscript of 1. Equal signs are used to represent =bold words=, and underscores are used to represent italics. On page 152 NaCO{23} has been corrected to Na{2}CO{3}. On page 212, the variable n has been replaced with the correctly subscripted forms n{1} and n{2}. The index entry for Hemlock bark had no page number in the original text, so the correct page number, 34, has been supplied. Ions are shown as Fe+++, instead of using superscripts. There is some inconsistency in the notation used in the original text for chemical formulae such as Na{2}Cr{2}O{7}(2H{2}O). These have been regularized to use the modern mid-dot, for example, Na{2}Cr{2}O{7}·2H{2}O. Greek letters in the original have been represented in this version by the name of the letter enclosed in square brackets, e.g. [alpha]. ANIMAL PROTEINS BY HUGH GARNER BENNETT, M.Sc. (LEEDS) MEMBER OF THE SOCIETY OF LEATHER TRADES' CHEMISTS; FORMERLY ASSISTANT LECTURER AND DEMONSTRATOR AT THE LEATHER INDUSTRIES DEPARTMENT OF THE UNIVERSITY OF LEEDS AUTHOR OF "THE MANUFACTURE OF LEATHER" LONDON BAILLIÈRE, TINDALL AND COX 8, HENRIETTA STREET, COVENT GARDEN 1921 (_All rights reserved_) GENERAL PREFACE