The study of the lymphatic system has a lengthy history, with many notable medical minds making important contributions. We now appreciate that this system is an essential component of the immune system, as well as vital to the maintenance of fluid homeostasis within the body. A good knowledge of the lymphatic system is clinically important concerning cancer, edema, surgery, and the immune response. This article reviews the history of the evolution and discovery of the lymphatic system.

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Lavall and colleagues deserve thanks for their excellent review article (1). The American guidelines (2) include as an additional criterion that any (one might wish to amend: greater than trivial) increase in distal aortic diameter should be categorized as a dilatation, independently of the absolute numeric value. If this was kept in mind by echocardiographers and attention as well as orientation of the transducer were routinely directed slightly distally, then in our own experience, they would find far more cases of (mostly hypertensive) aortic dilatation in an unselected patient cohort in a cardiology referral practice than has been assumed so far, especially in women and people of short stature.As far as the comparison of ultrasound and other values is concerned, I wish to point out that the values obtained by means of echocardiography (mostly the internal diameter) and computed tomography/magnetic resonance scanning (both the internal or external diameter are in use [2,3]) are not directly comparable and are furthermore subject to more than trivial intraindividual variation over the course of time.Assessment in the individual case is further complicated by the fact that the normal diameter of the aorta depends on a person's age (4). Defining the proper time for surgery is additionally hampered by the fact that the indication for surgery is graded according to absolute diameters (45-50-55-60 mm), whereas the normal ranges are sensibly indexed according to body surface area. It would be highly desirable for the medical specialty societies to establish clarity by relating the limits to the body surface area rather than absolute measurements of diameter.

The nice review by Klein und Trappe (1) should be supplemented by the data of Nuotio et al. (2). In a retrospective analysis of 5116 cardioversions without prior anticoagulation, thromboembolic events occurred only in 0.3% of patients when cardioversion was performed within the first 12 hours of atrial fibrillation. However, this rate increased to 1.1% when cardioversion was performed after more than 12 but less than 48 hours. The rate of thromboembolic events in the entire patient population was 0.7%, thus within the range of 0.3% to 0.8% reported elsewhere (3). In my view, the almost fourfold increase in risk of thromboembolic events observed when cardioversion is performed more than 12 hours after onset of atrial fibrillation indicates that it might be useful to review the practice of cardioversion without prior transesophageal echocardiography even after an atrial fibrillation duration of less than 48 hours and to initiate adequate oral anticoagulation therapy in all non-urgent cases with atrial fibrillation of more than 12 hours' duration.