This monograph deals with the physiologic and clinical significance of the lymphatic apparatus in mammals. It is a revision and extension of a previous monograph by Drinker and Field. The anatomic and physiologic organization of the lymphatic system, the permeability of blood capillaries and its relation to lymph formation, the functional significance of lymphoid tissue and the composition and flow of lymph are dealt with extensively and authoritatively. The necessity of a knowledge of the physiology of the lymphatic system to an understanding of numerous clinical problems, such as edema, inflammation and surgical shock, is clearly pointed out. The clinician will find much of value and the biologic investigator a wealth of stimulating ideas in this clearly written and well documented treatise.