THE CIRCULATION OF THE BLOOD 307 



several days or more. In the foregoing solution when the calcium chlorid 

 is present only to the extent of 0.026 per cent., though the ventricular strip 

 does not contract, it is kept in good condition for contraction, for even after 

 many hours the raising of the percentage of calcium chlorid to 0.04 or 0.05 

 per cent, will call forth after a brief latent period, rapid and energetic con- 

 tractions. From this fact it is inferred that the vena cava region is more 

 sensitive to the combined action of the salts than is the ventricle. 



The action of the individual salts is also best shown with ventricular strips. 

 In a 0.7 per cent, sodium chlorid solution the strip beats rhythmically and 

 energetically, but only for a short period and with gradually diminishing force, 

 and a loss of tonicity until it entirely ceases to beat. A reason assigned for 

 this is the removal of other salts necessary to the excitation of the contrac- 

 tion. In a calcium chlorid solution 0.9 per cent. i.e., isotonic with the 

 sodium chlorid the heart strip is thrown into strong tone, but does not 

 rhythmically contract. If, however, the strip is placed in normal saline, 

 and calcium chlorid added in amounts equal to that present in the blood, it 

 will after a very short period begin to contract rapidly and energetically and 

 for a longer time than when in sodium chlorid solution alone. The con- 

 tractions not infrequently occur before relaxation is completed, so that the 

 strip passes into the condition of contracture. 



In potassium chlorid solutions isotonic 0.9 per cent. with sodium 

 chlorid solution the heart strip also fails to contract. This is the case also 

 when the potassium is added to the sodium chlorid in amount practically 

 equal to that found in the blood. 



2. On the Mammalian Heart. The collective action of the inorganic 

 salts on the isolated heart of all members of this class of animals which have 

 been made the subject of experimentation, is as marked, if not more so, than 

 it is on the heart of the frog or terrapin especially when the coronary blood- 

 vessels are perfused with Ringer's solution or the modification of it suggested 

 by Locke, as follows: NaCl 0.90 per cent.; CaCl 2 0.024 per cent; KC1 0.042 

 per cent.; NaHCO 3 0.02 per cent., dextrose o.i per cent. The reviving and 

 sustaining power of this solution is extraordinary. Locke and Rosenheim 

 were able to revive the isolated heart of a rabbit and to excite it to active 

 contraction, for several hours at a time, on four consecutive days by perfusing 

 it with this solution saturated with oxygen and at a temperature of 35( 

 No special precautions were observed other than keeping it cool (ioC.) and 

 moist during the intervals of experimentation. The duration of the irrita- 

 bility and contractility extended over a period of 95 hours. Kuliabko 

 revived the heart of a rabbit for an hour nearly three days after removal from 

 the body of the animal. It was then placed on ice, and after four days i 

 was again revived by perfusing it with Ringer's solution. Altogether 

 heart retained its irritability for seven days. Hering revived the heart of a 

 monkey on three different occasions, the first, 4} hours, the second, 28 

 hours, and the third 54 hours after the death of the animal. In the inter- 

 vening periods the heart was also kept on ice. In this animal it was even 

 possible to increase and decrease the activity of the heart by stimulation of 

 the nerves which normally control the rate of the beat. Kuliabko was also 

 able to revive the isolated heart of a child 20 hours after death from a doubl 

 pneumonia. It was made to beat rhythmically at a rate varying from 70 to 80 

 per minute when the solution had a temperature of 3 9C., and at a raft 



