iv PREFACE 



These important new technological developments are presented in the chapters 

 about algae and seaweed products. 



Since 1923 our knowledge of the vitamins and amino acids has been greatly ex- 

 tended. Further, we now know a great deal more about the composition and 

 nutritive value of the fish, shellfish and fishery products used for food or medicine. 

 Further, large quantities of liver oils are now used for the making of vitamin con- 

 centrates. For these reasons it has been necessary to rewrite and greatly expand 

 the chapters dealing with the nutritive value of fishery products and the tech- 

 nology of fish liver and other oils. 



Fish meal has been found to be of greater value for animal feeding than was 

 formerly believed to be the case. Further, certain technological improvements 

 have made possible the production of meals of greater nutritive value. These 

 changes in the industry are indicated in the chapter on fish meal. 



References to the original literature, to comprehensive review articles, and to 

 worthwhile books, which will be helpful to those desiring more information than 

 that presented in this book, are appended at the end of each chapter. Literature 

 which was published prior to 1923 is not included unless the paper or treatise is of 

 exceptional importance. Those who wish to search the literature published before 

 1923 are referred to the First Edition of this book. 



The authors make no claim for originality for any of the theories or facts pre- 

 sented. All available sources of information have been freely consulted and com- 

 pared, and the latest information presented to the reader. 



The authors and their collaborators have attempted to have all of the material 

 presented accurate and up-to-date. Undoubtedly, unsuspected errors have crept 

 in. We desire to be advised of any erroneous statements noted, so that future 

 editions may be made more accurate. 



The book completed, the more pleasant task remains to thank the many persons 

 who have been so kind as to aid in its preparation. First, the authors wish to 

 thank their collaborators who have done so much to make this book a success. 



Special mention should be made of the following persons who have read parts 

 of the manuscript and have given many valuable suggestions for its correction and 



Mr. Fenner A. Chace Jr., U. S. Fish and Wildlife Service, Washington, D. C. 



Mr. R. E. Clark, Marine Magnesium Corporation, South San Francisco, Calif. 



Mr. Wm. A. Dumont, U. S. Fish and Wildlife Service, Washington, D. C. 



Mr. Gerald A. Fitzgerald, Fayetteville, New York 



Miss Florence E. Harris, U. S. Bureau of Mines, Washington, D. C. 



Mr. Earl C. Jertson, Krim-Ko Corporation, New Bedford, Mass. 



Mr. Frank T. Piskur, U. S. Fish and Wildlife Service, Washington, D. C. 



Mr. A. E. Power, U. S. Fish and Wildlife Service, Washington, D. C. 



Mr. R. Thevenot, Ministry of Agriculture, Paris, France 



Mr. WilHam R. Veasey, Dow Chemical Company, Midland, Mich. 



Dr. L. A. Walford, U. S. Fish and Wildlife Service, Washington, D. C. 



Dr. Claude E. ZoBell, Scripps Institution of Oceanography, La Jolla, Calif. 



In addition to those named above, many other persons, too numerous to men- 

 tion, have aided in the work. Many have furnished photographs used as illustra- 



