PREFACE. In the present monograph an attempt has been made to present the subject of the lipins in as simple a farm as the state of our knowledge permits. The task has been a difficult one, owing chiefly to the chaotic state of the literature dealing with these bodies the loose manner in which the term lipoid has been used has also added not a little to the general corfusion. A good deal of space has been given to a description of such alleged lipin substarlces as protagon and jecorin it was felt that a detailed discussion of these bodies was necessary in order that the reader might fully appreciate the very insecure and incoclusive evidence on which their existence as chemical entities had been based. Much of the monograph was written under adverse conditions, and more especially was this the case with Chapter VIII. which deals with the biological aspect of the subject. Before this chapter could be finished I was called to France, and was faced with the alternative of postponing the...