Serous fluid major salivary glands produce mixed (serous and mucus) saliva. Another type of serous fluid is secreted by the serous membranes (serosa), two-layered membranes which line the body cavities. Serous membrane fluid collects on microvilli on the outer layer and acts as a lubricant and reduces friction from muscle movement. This can be seen in the lungs, with the pleural cavity. Blood serum is the component of blood that is neither a blood cell, nor a clotting factor. Blood serum and blood plasma are similar, but serum does not contain any clotting factors, such as fibrinogen, prothrombin, thromboplastin and many others.
Blood, toil, tears, and sweat are "It [poetry] is forged slowly and painfully, link by link, with blood and sweat and tears" (Lord Alfred Douglas, 1919), "Blood, sweat, and tear-wrung millions" (Lord Byron, 1823), and "...mollifie/ It with thy teares, or sweat, or blood" (John Donne, 1611). In Latin, Cicero and Livy had used the phrase "sweat and blood". "We are in the preliminary stage of one of the greatest battles in history... That we are in action at many points—in Norway and in Holland—, that we have to be prepared in the Mediterranean. That the air battle is continuous, and that many preparations have