254 JOSEPH C. AUB 



overwhelming infection (such as gas gangrene). The differential diag- 

 nosis of the primary condition is, therefore, often a difficult one. 



Theories of Shock 



Many attempts have been made to explain the phenomena found in 

 shock, and there are many theories as to its cause. Crile (6) believes that 

 painful stimuli cause an exhaustion of the cells of the central nervous 

 system, and that a resulting failure of the vasomotor center causes the 

 low blood pressure. Yandell Henderson (a) thinks that the excessive stim- 

 ulation and pain cause hyperpnea. As a result there is a marked reduc- 

 tion of CO 2 in the blood, and this in turn induces vasodilatation and a fall 

 in blood pressure. Porter has advanced the theory that trauma releases 

 fat droplets into the circulation droplets which cause fat emboli in the 

 lungs and central nervous system, and lead to a fall of arterial blood 

 pressure by preventing venous return to the heart, and by affecting the 

 higher nerve centers. Cannon and Bayliss, in a series of very interesting 

 experiments, showed that shock could be produced by crushing large areas 

 of muscle tissue. A fall of blood pressure followed the crushing in about 

 twenty or thirty, minutes and was usually progressive. Shock developed 

 even though the wounded area had its nerve supply cut, but did not develop 

 if the blood supply was tied. The conclusion from these experiments 

 was that shock was a toxemia, due to some substance arising in the in- 

 jured tissues. At about the same time that these experiments were in 

 progress, Quenu and his collaborators were arriving at a similar con- 

 clusion, by investigations on soldiers wounded at the front. 



Pathological Physiology of Shock 



From this brief review of the theories of the cause of shock, and of 

 the accompanying phenomena, it becomes clear that the primary cause 

 of the condition is far from being determined. This, however, is not true 

 of the various phenomena which may either precede or accompany the 

 development of traumatic shock. Great advances have been made in 

 our knowledge of these conditions during the past few years, largely cjuring 

 the last two years of the recent World War. The wisest procedure is 

 probably to study the various accompanying phenomena in the order in 

 which they occur. The most striking phenomenon which has been observed 

 for many years in shock is that the patient seems quite exsanguinated. 

 Previous to the recent war it was generally considered that the blood was 

 stagnating in the abdominal vessels. The testimony of many surgeons, 

 who had large experience during the war, was that the blood was not in 



