Increase in the number of leucocytes in the blood.
An increase in the numbers of leucocytes in the blood above the usual upper limit, in order to fight an infection.
A condition in which the polymorphonuclear leucocytes in the blood are increased in number. It occurs in many different circumstances, and forms a valuable means of diagnosis in certain diseases; the condition may, however, occur as a normal reaction in certain conditions (e.g. pregnancy, menstruation, and during muscular exercise). It is usually due to the presence of inflammatory processes the increased number of leucocytes helping to destroy the invading bacteria. Thus, during many acute infective diseases, such as pneumonia, the number is greatly increased. In all suppurative conditions (where PUS is formed) there is also a leucocytosis, and if it. seems that an abscess is forming deep in the abdomen, or in some other site where it cannot be readily examined —as, for example, an abscess resulting from appendicitis the examination of a drop of blood is a valuable aid to diagnosis.