THE METABOLISM OF TRAUMATIC SHOCK 255 



the large veins of the abdomen, that these veins, in fact, appeared quit as 

 devoid of blood as the vessels of the rest of the body. 



Where, then, is the blood ? The first work which offered a suggestion 

 for the answer of this problem was done by Cannon and collaborators in 

 Bethune. They found that the blood in the capillaries of the periphery 

 was more concentrated than that in the veins, and that the red count 

 from these capillaries was very much higher than the count taken from 

 the veins. This suggested that the fluid of the blood was leaving the 

 circulation and going into the tissues. That the volume of blood actually 

 does decrease has been very beautifully shown by Keith on human beings, 

 and by Gasser, Erlanger and Meek on aninlals. These latter observers 

 have also shown that the protein content of the plasma is not changed 

 by the process of concentration. It therefore seems clear that the plasma 

 as a whole leaves the circulation. This reduction of blood volume which 

 has still not been explained may of itself explain the resulting phenomena 

 which develop. 



The first effect of the diminished blood volume seems to be to affect 

 markedly the blood flow to certain parts of the body. Gesell (&) showed in 

 very interesting experiments the marked slowing of blood flow through 

 the salivary glands, not only in shock, but also following the withdrawal 

 of blood, even when this did not lower the blood pressure. This fact 

 suggests that the resulting vasoconstriction, though satisfactory in keep- 

 ing up the blood pressure to its normal level, still has as an effect the 

 marked slowing of the blood flow at least through some tissues. If the 

 blood volume continued to fall, the next effect was a drop in blood pressure. 

 Wiggers also showed, by optically recorded blood pressure studies, that 

 the effects upon the circulation in .shock might appear before a low blood 

 pressure level was reached. As the blood volume continues to decrease a 

 fall of blood pressure results, which may reach the low level of 50 or 

 60 mm. Hg, frequently found in shock. With this fall in blood pressure, 

 and the resulting decrease in the force of propulsion through the capil- 

 laries, the blood flow naturally continues to decrease in speed. One effect 

 of this slowed blood flow and reduced blood volume must be to reduce the 

 amount of oxygen available for the use of the tissues. 



That the oxygen available for the tissues is markedly reduced in shock 

 was first demonstrated by Yandell Henderson (a). He showed that in ex- 

 perimental shock the venous blood had far less oxygen than had the venous 

 blood before shock, and arrived at the conclusion that the oxygen supply 

 available was inadequate for the tissues. This work has been recently 

 confirmed by Aub and Cunningham, who also found that this decrease 

 in available oxygen is seen before the blood pressure reaches the shock 

 level of 80 mm Hg. Fig. 1 pictures graphically the magnitude of this 

 change in the venous oxygen content. By mechanically preventing the 

 normal blood flow through increasing pericardial tension, Aub and Cun- 



