PERFUSION OF HEART 71 



as digitaline and veratrine, can bo studied by adding definite amounts of thcso 

 to the Ringer's solution used for perfusion. For such purposes it is convenient 

 to have two reservoirs of Ringer's solution (fig. (51), one for addition of the 

 drug to be investigated, and the other to flush out the heart after the action 

 of the drug is complete. Both reservoirs are connected with the inflow of the 

 cannula by a three-way tube (e) furnished with a stop-cock or with small flips. 



Influence of calcium and potassium on the cardiac contractions : Ringer's 

 experiment. Place in the second reservoir a solution containing 6 parts of pure 

 Nad to 1000 of distilled water, and keep it filled with this solution. Flush the 

 heart with it ; the organ will soon cease to contract and to respond to excitations. 

 Now mix with the 100 c.c. of fluid in the second reservoir 2 c.c. of a 1 per cent, 

 solution of calcium chloride and flush the heart with the mixture. Contractions 

 will be resumed, but each one will be too prolonged, and the heart will again 

 soon stop : this time in systole. Next add 4 c.c. of a 1 per cent, solution of 

 potassium chloride to the contents of the second reservoir, mix thoroughly, 

 and flush the heart With the mixture. The beats will recommence, either 

 spontaneously or in response to stimulation, the normal character being 

 resumed. If the potassium salt is added in excess, the heart will be arrested 

 in diastole. 



Perfusion of the heart in situ. In large frogs the heart can be perfused in situ 

 by introducing a very fine glass or metal cannula into the vein which runs along 

 the middle line of the ventral wall of the abdomen. The vein is exposed by 

 making a longitudinal incision through the abdominal wall a little to the right 

 of the middle line, and a transverse incision at the level of the ensiform cartilage 

 starting from the upper end of the longitudinal cut and carried outwards. The 

 triangular flap thus made is turned down, and the vein will be seen passing 

 from the abdominal wall towards the heart. The cannula is connected with a 

 reservoir of Ringer's fluid, which is allowed to drop very slowly from its end 

 during insertion, so that no air-bubbles can enter. It is then tied in, and the 

 heart, previously exposed and attached to a heart lever (as in fig. 60), is flushed 

 with the solution, which is allowed to flow out from a small cut near the apex of 

 the ventricle. Drugs are introduced by means of a second reservoir as before. 



Perfusion of the mammalian heart. The heart is excised from a recently 

 killed cat or rabbit, and the aorta is at once tied on to a cannula through which 

 Ringer's solution, saturated with oxygen, is slowly dropping. The solution is 

 warmed to about 38 C. before reaching the heart which is itself kept in a 

 warmed chamber. The cannula is directed towards the aortic valves, which are 

 closed on raising the pressure of the perfused fluid ; this runs through the 

 coronary vessels and escapes through the right auricle. The amount of fluid 

 perfused can be measured by a tilter (see p. 87). The contractions of the heart 

 can be recorded by one or more light levers, attached to it by threads which 

 are passed over pulleys. The action of drugs is investigated by adding them to 

 the Ringer's solution. 









