The word shock as currently used covers essentially the following conditions:
1. Primary shock, characterized by direct reduction of blood pressure and other less precisely defined acute symptoms, attributed to nervous, circulatory or toxic causes.
2. Secondary shock, a more slowly developing condition, of better defined character but of disputed etiology. It has usually been produced experimentally by mechanical, thermal or other trauma of the limbs or of the intestine. Authorities are agreed as to the epochal importance of the physical concept, established by Phemister,1 Blalock2 and their collaborators and corroborated by numerous writers (Herbst,3 Holt and Macdonald,4 Harkins5 and his collaborators, Underhill6 and his collaborators, Roome and Wilson,7 Aikawa8 and others) through demonstration of a passage of protein-containing fluid resembling blood plasma into the injured tissues, with consequent increase of corpuscle counts and reduction of volume of the blood. The opposite