Methods of Raising a Loiv Arterial Pressure. 391 



Arterial pressure 41 mm. of mercury. Heart beats very small. Three cubic 

 centimetres of 0-04-per-cent. barium chloride given intravenously ( = 1 mgrm. 

 per kilogramme). Pressure raised to 63 mm. Twenty cubic centimetres of 

 gum solution were tben given. The pressure was raised to 96 mm. It 

 remained high for 7 or 8 minutes, but slowly fell, until in 27 minutes it was 

 54 mm. A further dose of barium chloride did not raise the pressure much. 

 The vaso-constrictor mechanism was found finally to respond to asphyxial 

 stimulation. 



It appears that in physiological experiments the injection of barium 

 chloride combined with gum solution will be found useful. Whether it 

 would be admissible for clinical use, I am unable to state. 



Accommodation of the Vascular System. 



Some incidental observations made in the course of the preceding research 

 are of interest. 



It has long been known that after haemorrhage there is a gradual rise of 

 blood pressure, and also that an artificially produced rise of pressure causes a 

 reflex vaso-dilatation. The latter is generally regarded as due to stimulation 

 of receptor endings of the depressor nerves. Heidenhain appears to have 

 thought that the vasomotor centres are directly sensitive to rise and fall of 

 arterial pressure. But very little direct evidence has been obtained towards 

 solution of the problem. Johansson and Tigerstedt (15) state that loss of 

 blood results in vaso-constriction, but I have been unable to find the 

 experimental evidence in their paper. 



Clearly the only way in which direct evidence can be obtained is by 

 observations on the state of the arterioles in an organ whose circulation is 

 independent of that of the animal to which it belongs, while it is still in 

 nervous connection therewith. Experiments of this kind have been made by 

 Pilcher and Sollinann (16) on artificially perfused spleens. They found that 

 haemorrhage caused vaso-constriction, transfusion of blood caused vaso- 

 dilatation. 



The question seemed of sufficient importance to warrant further experi- 

 ments, and on another organ. I chose the hind leg of the cat. The whole 

 of the tissues, excluding the femoral artery and vein and the nerves, were 

 tied off by a series of strong ligatures. As perfusion fluid, 7-per-cent. gum 

 in Einger's solution was used. This was aerated by blowing air through it 

 and was driven through the limb under constant pressure by means of a small 

 pump. A side outlet on the delivery side served to keep the pressure 

 constant and was adjusted by means of a screw pinchcock. The pressure was 

 also controlled by a manometer attached to the cannula in the femoral artery. 



vol. lxxxix. — b. 2 I 



