The entrances to the digestive and respiratory tracts are exposed to many pathogenic micro-organisms and are guarded by the adenoids, the tonsils and the lymphatic tissue on the tongue, forming the ring of Waldeyer. Particularly in young persons these structures can easily become swollen during an infection. When the lymphatic structures are chronically infected, they no longer act as a defence mechanism, but as a constant source of infection. Then they are removed. Their removal however is nowadays not as lightly undertaken as it was about 20 years ago, because doctors now consider these lymphatic structures to be very important to our defence system.