214 THE CIRCULATION OF THE BLOOD AND LYMPH 



(p. 212). Connect the carotid with the manometer, and the femoral 

 vein with a burette or large syringe containing the peptone solution. 

 Take care that the connecting-tube and cannula are free from air. 

 Now commence to take a blood-pressure tracing, and while it is going 

 on inject the peptone solution. The pressure falls owing largely to 

 a dilatation of the small arteries through the direct action of the pep- 

 tone on their muscular tissue or on the endings of the vaso-motor nerves.* 

 28. Effect of Suprarenal Extract on the Blood-Pressure. Make the 

 arrangements for a blood-pressure tracing from a dog as in 23 (p. 208). 

 Put a cannula in the carotid and another in the femoral vein or one of 

 its branches (p. 212). Expose both vagi in the neck, and pass threads 

 loosely under them. Connect the carotid with the manometer and 

 take a tracing. Then, while the tracing is continued, inject slowly 

 into the femoral vein an amount of watery extract corresponding to 

 about 0*2 grm. of suprarenal, or, what is more convenient, a few c.c. 

 of a solution of adrenalin chloride of the strength of I to 50,000 in 

 0*9 per cent/ sodium< r chloride solution, the dose depending, of course, 

 on the size of the animal. The blood-pressure risesf owing to con- 



Fig. 106. Effect of Injection of Peptone on the Blood- Pressure in a Dog. 

 (To be read from right to left.) 



striction of the arterioles by direct excitation of the junction between 

 their vaso-constrictor nerves and their muscular tissue. The heart is 

 slowed, but its beat is strengthened. At once cut both vagi while a 

 tracing is being taken; the blood-pressure rises still more (p. 638). 

 The rise of pressure is sometimes so great that to prevent the mercury 

 from being forced out of the manometer the tube must be clipped. 

 The rise is not long maintained, but a second injection causes a renewed 

 increase of pressure. 



29. Action of Epinephrin (Adrenalin) on Artery Rings. The experi- 

 ment (8) described on p. 66 in connection with the constrictor action 

 of serum may equally well be performed here. 



* In 12 dogs the blood-pressure always fell, the amount of the fall varying 

 from 8 1 to 21 mm. of mercury (average, 60 mm.). It sometimes returned to 

 normal in twenty to thirty minutes, but usually required a longer time. In 

 some dogs, after the injection of the whole of this amount of peptone, death 

 occurs before there has been any considerable recovery of the pressure. 



f The amount of the initial rise of pressure is very variable, since the slow- 

 ing of the heart tends to diminish the pressure, while the constriction of the 

 arterioles tends to increase it. Thus, in one experiment the increase of pres- 

 sure on injection of the extract was only 6 mm. of mercury, while in another 

 it was 56 mm. On section of the vagi in this second experiment, there was 

 an additional rise of 64 mm., and after a second injection a further rise of 

 70 mm., making an increase of 190 mm. in all above the original pressure. 



