8 4 



Scientific Proceedings (64). 



the number of deaths of the animals of one series as compared to 

 the results of the experiments of another series in which the ani- 

 mals were rendered slightly less sensitive to shock though subjected 

 to precisely the same severity of stimulation, to determine the in- 

 creased shock-producing effect of the electrical stimulation of their 

 sensory nerves. 



By passing a loop of thread around the inferior vena cava 

 through a small incision in the chest wall, and sewing up the 

 incision in such a manner that the loop of thread emerged in a 

 straight line through the incision, a means was provided of so 

 limiting the amount of blood returned to the heart that the arterial 

 blood pressure could be reduced to any desired degree and for any 

 length of time. At the conclusion of the experiment, one strand 

 of the loop of thread was divided and the loop removed without 

 additional operative procedure, or the danger of pneumothorax, 

 and without any anatomical abnormality remaining. 



Such a method furnished a convenient means of reducing the 

 general blood pressure without, — it was assumed, — producing other 

 deleterious effects on the animal than those resulting from the 

 reduction of blood pressure alone. A number of preliminary 

 experiments were devoted to ascertaining the level below which it 

 was dangerous to reduce the blood pressure for a period of two 

 hours. This level was — roughly — 40 to 50 mm. of mercury. 

 Having approximately ascertained this level, twelve experiments 

 were performed in which the blood pressure was reduced for a 

 period of two hours, so that the pulse pressure varied 



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

 " 20 to 30 " " " " 3 



40 to 50 " " " " 1 animal. 



Of these animals, 9 died and 3 recovered. Of the animals 

 which recovered, the pulse pressure of 2 varied between 20 to 

 30 mm. ; and of one, between 30 to 40 mm., for the two-hour period 

 during which the blood pressure was mechanically reduced. 



A very important fact which possesses a significance with the 

 true nature of shock, concerns the character of the blood pressure 

 curve after the removal of the loop around the inferior vena cava. 

 The height to which the blood pressure rises immediately after the 



