Influence of Nocuous Stimuli in Shock. 



85 



release of the ligature is inversely proportional to the fall pro- 

 duced by the ligature. In some dogs it will return to the normal 

 height soon after the experiment and maintain a good height for 

 three to four hours, and then begin to progressively fall until 

 death. 



These twelve experiments, therefore, constituted the controls. 

 With them were compared the additional effect produced by 

 strong electrical stimulation of the peripheral sensory nerves in 

 two other series of animals. 



In one of these series, the strong electrical stimulation was 

 applied during a period in which the animals' blood pressure was 

 reduced to the same critical degree as in the control series and for 

 the same length of time, i. e., 2 hours. In the second series, the 

 electrical trauma was applied during a period in which the blood 

 pressure was reduced to a level which was considered just above 

 the danger line, i. e., 40 to 50 mm. of mercury. 



The electrical stimulation was applied from an inductorium 

 to the central end of both sciatic nerves. By an automatic ar- 

 rangement, an attempt was made to eliminate block from fatigue 

 and localization, by alternately switching the current from one 

 nerve to the other. All experiments lasted two hours, and this 

 period was selected because it corresponded to the usual duration 

 of a long operation on the human being. 



There were 13 experiments in which the electrical trauma was 

 applied during a two-hour period of a low'reduction of blood pressure. 

 Of these animals, one alone recovered. In this recovered animal, 

 the pressure varied between 20 to 30 mm., — in other words, a 

 very low level. Of those that died, the pulse pressure varied 



Between 30 to 40 mm. of mercury in 8 animals, 



20 to 30 " " " " 1 animal, and 

 40 to 50 " " " " 3 animals. 



In interpreting the results of this series, some allowance must 

 be made for the greater difficulties of the experiments in the stimu- 

 lated series as compared with the controls. In the former, much 

 more ether was necessary. Throughout the experiment, even 

 though the animals were unconscious, it was difficult to control 

 the struggling and there was constant hyperpnea; moreover, it 



