342 PRACTICAL PHYSIOLOGY 



When the heart is completely restored replace the Ringer's solution 

 with normal saline solution -65 per cent, in distilled water. The heart 

 will after some time become weaker, and finally stop in diastole. Water 

 distilled in glass is less noxious than water distilled in copper or lead. 

 Merely hanging a strip of copper foil in distilled water over-night 

 increases its poisonous properties. It is calculated that there is not 

 more than 1 part of copper in 70 million of the water. Tap-water 

 contains traces of calcium salts, which are beneficial. Normal saline 

 should therefore be made with tap-water. An isotonic solution of KC1 

 0*9 per cent, arrests the heart. A 2 per cent, solution of digitalin 

 causes increased tone of the heart, vigorous systole, and incomplete 

 diastole. The heart finally is arrested in a state of systolic contraction. 

 Caffeine and veratrine also act tonically on the heart. 



Supra-renal extract, or adrenalin, at first slows and then increases the 

 tone and the frequency of the heart. It is an antidote to the effect 

 of chloroform on the heart. Adrenalin is the active principle of the 

 medulla of the supra-renal gland, separated by Takamine. A solution 

 containing 1 part in 10,000 constricts vessels of the conjunctiva. 



Weak solutions of acid bring the heart into diastolic arrest. Alkalies 

 produce systolic arrest. 



CHAPTER XXIII. 



THE CARDIAC PLETHYSMOGRAPH. THE EFFECT OF TEMPERA- 

 TURE ON THE HEART. CARDIO-PNEUMATIC MOVEMENTS. 



Schafer's Plethysmograph. The double cannula is fitted with two 

 rubber tubes, and clips are placed on these. The cannula and the 

 tubes are filled with Ringer's fluid. One of the tubes ends in a syphon 

 tube which dips into a flask containing Ringer's solution. The heart 

 is now exposed, and a slit made in the left auricle with fine scissors. 

 The scissors are passed into the ventricular cavity, and two or three 

 snips are made so as to clear a way in the muscular mesh work within the 

 cavity. The cannula is then inserted, and a ligature is tied round the 

 auricles, including the cannula. The plethysmograph is filled with 

 olive oil. The tap on the overflow tube is opened and the cannula is 

 inserted. This tap is then closed, and the tap leading to the piston 

 recorder opened. The clips on the cannula tubes are opened, and the 

 beaker raised a few inches above the level of the heart so as to main- 

 tain an efficient flow to the heart. The piston records the contractions 

 on the horizontal drum (slow rate) 



