ADVANCED EXPERIMENTAL PHYSIOLOGY 153 



2. 0-75% NaCl solution containing 0-3% KC1 (5 c.c. 7% KC1 

 solution in 100 c.c. 0*60 NaCl) followed by Ringer or Locke's 

 solutions until the normal beat is recovered. 



3. 0'75 % NaCl solution containing a few drops of a 5 % solution 

 CaClo followed by Ringer or Locke's solution until normal beat is 

 recovered. 



4. Distilled water. 



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. The heart 

 is at first stimulated by sodium ions, but after some time becomes 

 weaker, and finally stops in diastole. Tap-water contains traces of 

 calcium salts, which are beneficial. Normal saline should therefore be 

 made with tap-water. The calcium ions present in small quantities in 

 the blood help to maintain contractility and irritability. Excess of 

 calcium throws the heart into a contracted state calcium rigour. 

 Potassium ions in excess relax the heart and abolish excitability. 

 Ringer's solution contains 0-7 % NaCl, 0-03 % KC1, 025 % CaCl, and 

 keeps the heart in good state. 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. Adrenalin is the active principle of the 

 medulla of the supra-renal gland. 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. 



