The commonest, and fastest, way in which pathogens can spread through the body is via the bloodstream.Moreover, tissue fluid can drain directly into lymphatic vessels.However, individual pathogens show a preference to localise in particular organs or tissues that may differ from pathogen to pathogen .The lymphatic vessels form a circulatory system that parallels that of the blood .The circulation of the lymphatic fluid is maintained not by the heart but by the movement of the muscles surrounding the lymphatic vessels; thus lymphatic fluid flows at a much more sluggish rate than blood.