hen I took up my studies on semen in 1944, on behalf of the Agricultural Research Council, I became painfully aware of the fact that information on the physiology of semen, its chemical aspects in particular, is rather difficult to come by; the older observations and records being hidden away in books and journals not readily accessible in any but the best equipped libraries, and moreover, scattered throughout an exceptionally wide range of publications, which embrace disciplines as far apart as say, agriculture, urology and cytology. Judging from numerous requests for information, received from fellow workers in the field, biochemists, clinicians, zoologists and veterinary officers alike, the absence of a fairly comprehensive and up-to-date treatise on the chemical physiology of semen must have proved a serious handicap to many in their scientific and practical pursuits. Therefore, I accepted gladly the invitation to write this book; having agreed to produce but a 'little book', I have often found it rather irksome to condense the vast mass of data into the allotted space; had it not been for the encouragement and ready help of colleagues-my wife not least among them, the task would have been even more burdensome. Biochemistry of semen is a relatively modern, but rapidly expanding, field of physiology; consequently, many of our present views, particularly as regards the biological significance of various chemical constituents of semen, may have to be revised or modified in the near future. That being so, I like to look upon this book, or at any rate, those parts of it which deal with the newer, still fluid concepts, as something in the nature of an Interim Report, designed to furnish information and to convey ideas emerging from the state of knowledge as available at the time of writing, however imperfect that may be. In presenting the recently acquired evidence, I have tried to render justice to developments in the sphere of mammalian as vi The Biochemistry of Semen well as non-mammalian physiology, selecting examples from species as far apart as man and the sea-urchins, and occasionally, introducing plants as well. I have done my best to distinguish between established fact and tentative hypothesis, and, as far as possible, have refrained from the tendency, currently prevalent among workers in this field, to assign to every newly discovered chemical constituent of semen a major role in the process of fertilization. I wish to acknowledge gratefully the help of those who gave me permission to reproduce plates and figures. In particular 1 wish to extend my thanks to Dr.
