The central factor in the production of traumatic shock is the reduction of the volume of blood. The exact mechanism of the oligemia occurring in shock is debatable, but at the present time most consideration has been given to three hypotheses. According to the first, vasotropic substances are formed in the area of injury and are absorbed into the general circulation, producing a marked fall in the blood pressure and an increase in the permeability of the capillaries. As a result, blood and blood plasma pass out into the extravascular tissues, and a reduction in the volume of blood takes place (Cannon,1 Cannon and Bayliss2 and Grunke and Haring3).
Subsequent observers, however, have been unable to obtain convincing evidence of the presence of such toxic products either in the area of injury (Blalock,4 Parsons and Phemister5 and Simonart6) or in the blood stream of