GRAPHIC OF ARTERIAL PRESSURE 28 



The other branch of the glass T-piece is armed with about 50 cm. length 

 of thick-walled rubber tubing of about 4 mm. bore. This is the junctional 

 (j) tube. On it, about 2 cm. from its free end, is a small screw-clamp (l). 

 See that this tube is cleanly washed out with fluid from the pressure-reservoir, 

 and clamp it. 



Make sure that there is no air caught in the column of fluid between 

 the Hg in the proximal limb of the manometer and the junctional tube. 

 If there is, get it out by opening the clamp (a) on the top of the proximal 

 limb of the manometer and allowing fluid from the pressure-bottle to drive it 

 up. This done, close the clamp on the top of the proximal limb of 

 manometer. The pressure-bottle is now to be pulled up to a height which 

 depresses the Hg in the proximal limb of the manometer 8 cm. below that in 

 the distal ; then close the clamp on the rubber tubing from the pressure- 

 bottle. Squeeze the junctional rubber tubing briskly once or twice between 

 finger and thumb and see that the Hg column oscillates freely and that the 

 float rides on it freely and does not stick or plunge. The distal limb of the 

 manometer must be quite dry and clean. See that the glass-pen carried by 

 the float (f) writes clearly on the kymograph paper. To ensure this the 

 manometer must be brought close to the kymograph and the weighted 

 guide-thread hanging from the kymograph must be duly adjusted to keep the 

 glass-pen against the sooted paper. Inverted as a cap over the top of the 

 distal limb of the manometer is a bit of wider glass tube drawn to a point 

 and then broken there. This serves as the lower guide for the float. See 

 that the height at which the pen writes is such that there is clear room 

 for a fall of 4 cm. and for a rise of 4 cm. This is to be done by adjusting the 

 height of the kymograph paper, not by altering the height of the manometer 

 stand ; the latter should be so placed that when the Hg columns of the two 

 limbs are of equal height their tops should be about on the same level as the 

 heart of the preparation on the experiment table. The manometer and its 

 tubing are now ready for use. 



(4) See that the kymograph runs at a speed that carries the recording 

 paper about 1 cm. in 3", and in a direction from right to left as you face it. 

 See that the time-signal marking seconds works and that the signal for 

 marking the period of stimulation marks. Both should be so placed as not to 

 hamper the record of the manometer. It is important to know the ' longi- 

 tude ' of the stimulation-marker in relation to that of the manometer-pen's 

 mark. To record this, set the kymograph running for a cm. or so, then 

 stop it ; then squeeze the junctional tube so as to make a vertical mark with 

 the manometer-pen and then close and open the stimulation-marker circuit. 

 The marks made by the two should be as nearly as practicable in the same 



