188 A MANUAL OF PHYSIOLOGY 



Connect the first cannula with a manometer, arranged to write on 

 a drum as in experiment 19 (p. 185). Take the bulldog off the 

 carotid, and measure the difference in the level of the mercury in the 

 two limbs of the manometer with a millimetre scale. 



(1) (a) While a tracing is being taken, draw off about 10 c.c. of 

 blood from the femoral artery, and observe whether there is any 

 effect on the tracing. Mark on the tracing the moment when the 

 removal of the blood begins and ends. 



(b) Repeat (a), but run off about 100 c.c.* of blood, and let this 

 be immediately defibrinated. Then draw off portions of 100 c.c.* 

 at short intervals until a distinct fall of blood-pressure has been pro- 

 duced. All the samples of blood should be defibrinated. 



(2) (a) Now, while a tracing is being taken, inject the whole of 

 the defibrinated blood slowly through the cannula in the femoral 

 vein by means of a funnel supported by a stand at such a height that 

 the blood runs in easily. A pinchcock should be put on the tube 

 connecting the funnel and the cannula, and this should be closed 

 before the funnel is quite empty, so as to obviate any risk of air 

 getting into the vein. Of course, the cannula and connecting-tubes 

 must all be freed from air before injection is begun. Again measure 

 the difference in the level of the mercury and compare the pressure 

 with that observed before the first haemorrhage. 



(b} Inject into the vein, while a tracing is being obtained, about 

 100 c.c. of normal saline*solution heated to 40 C., and go on 

 injecting portions of 100 c.c. until a distinct rise of pressure has taken 

 place, keeping a record of the total amount injected, and marking the 

 time of each injection on the curve. 



(c) After an interval of thirty minutes, again measure the height of 

 the mercury in the manometer. Then bleed the dog to death while 

 a tracing is being recorded. 



22. The Influence of Albumoses on the Blood-pressure Albu- 

 mose (* Peptone ') Plasma. Set up the apparatus for taking a blood- 

 pressure tracing as in experiment 19, but omit the induction coil. 

 Weigh a dog. Weigh out a quantity of Witte's peptone equivalent 

 to 0*5 gramme for every kilo of body- weight. Dissolve the peptone 

 in about ten times its weight of normal saline solution. Anaesthe- 

 tize the dog with morphia and ether or ACE mixture. Put cannulae 

 into the central end of one carotid, of one crural artery, and of 

 the crural vein on the opposite side. Connect the carotid with the 

 manometer, and the femoral vein with a burette or large syringe 

 containing all the peptone solution except 15 drops, which are put 

 into a test-tube labelled A. Take care that the connecting-tube and 

 cannula are free from air. Label another test-tube B. Run into 

 both test-tubes about 5 c.c. of blood from the femoral artery, and set 

 them aside. Now commence to take a blood-pressure tracing, and 

 while it is going on, quickly inject the peptone solution. Notice the 

 effect on the tracing. The pressure falls owing largely to a dilatation 

 of the small arteries through the direct action of the peptone on their 

 muscular tissue or on the endings of the vaso-motor nerves. As 



* 200 c.c. for a large dog. 



