πλάσμα

Plásma comes from Greek plassein (to mold, to form). The word meant something molded — a figure, a fabrication, a formed thing. The Czech physician Jan Evangelista Purkyne used it in 1845 for the liquid component of blood — the straw-colored fluid that remains when all the cells are removed. Purkyne saw the plasma as the matrix, the formless base from which the formed elements (red cells, white cells, platelets) emerged.

Blood plasma constitutes about 55 percent of blood volume. It is 92 percent water, with the remaining 8 percent consisting of proteins (albumin, globulins, fibrinogen), electrolytes, nutrients, hormones, and waste products. Plasma is not simply leftover fluid. It is a sophisticated solution that carries everything the blood cells do not. Without plasma, blood would be a pile of cells with no transport medium.

The physics meaning of plasma — the fourth state of matter, an ionized gas — was introduced by Irving Langmuir in 1928. Langmuir saw the ionized gas carrying suspended particles and thought of blood plasma carrying suspended cells. The analogy was deliberate: both are matrices in which other things float. Stars are made of plasma. Lightning is plasma. The northern lights are plasma. The word went from blood to the cosmos.

Blood plasma transfusion, developed during World War II, saved millions of lives. Dried plasma could be stored and transported without refrigeration, unlike whole blood. Charles Drew, an African American physician, organized the first large-scale blood bank and plasma processing programs. The Greek word for 'something formed' became the word for something that saves the formless — the wounded, the dying, the bleeding.