1881.] On the Physiological Action of ft Lutidine. 163 



The three chief ones were — 

 (a.) Moist chamber and lever ; 

 (/3.) Roy's apparatus ; 



(7.) Gaskell's method of the excised heart. 



(a.) Moist Chamber and Lever. — In this method the frog had jnst 

 sufficient of its skin and sternal cartilage removed to expose the apex 

 of the heart ; a carefully balanced lever (of the first kind) had attached 

 to one end of it, by a horizontal pivot, a light needle, which, by means 

 of a small piece of cork, just rested upon the apex of the heart. The 

 other end of the lever carried a fine piece of aluminium to mark the 

 beats upon the smoked surface of a revolving cylinder. Another 

 piece of aluminium recorded the abscissa line from which variations 

 in the height of the curve of ventricular beats could be recorded. A 

 glass shade, having a slit to allow the end of the lever to protrude 

 and work upon the drum, was then placed over the animal, and the 

 air inside kept moist with damp blotting-paper. 



From the arrangement of the apparatus it is evident that at each 

 ventricular systole the marker would fall, and at each diastole rise; 

 any increase in the tonicity of the heart being indicated by the tracing 

 approaching the abscissa line. 



A tracing of the heart's normal beat was in all cases first taken, 

 and then various quantities of various strengths of (3 lutidine were 

 injected into different parts of the body, from a drop or two of 2 per 

 cent, solution in the lymph spaces near the heart, to 0*2 cub. centim. 

 of 2 per cent, in the lower part of the abdominal cavity. In all cases 

 there was a very evident lowering of the lever's marking point and a 

 decrease in the size of the beats, clearly showing that the heart had 

 experienced a distinct increase in its tonicity. In all cases it became 

 much paler. 



No. I is a characteristic series of tracings showing the alterations in 

 the ventricular beats. Of these (1) is that made by the normal heart, 

 while 2, 3, and 4, were taken at intervals of one, three, and six minutes 

 after the injection of 0*2 cub. centim. of 2 per cent, lutidine into 

 the abdominal cavity. The increase in tonicity and slowing of the 

 beat are most evident. These tracings should be read from right to 

 left, a a being the abscissa line. 



(/3.) Boy's Apparatus. — In this apparatus the heart is tied upon a 

 double canula, one limb of which is in connexion with a supply of fresh 

 diluted sheep's blood (one part of defibrinated blood to three parts of 

 0*75 per cent, saline solution), kept at a constant height in a reser- 

 voir ; the other allowing the blood as it is pumped off by the heart to 

 flow away. The surface of the fluid in the reservoir being always 

 at the same height, variations in the heart's beat could in no way be 

 due to variations in pressure of the fluid. The heart tied to the 

 canula is inserted into a closed chamber filled with oil. By a par- 



