i88 



A MANUAL OF PHYSIOLOGY 



B\y 



FlG. 83. MYOCARDIOGRArH OF ADAMI AMD ROY 



(MODIFIED BY CUSHNY AND MATTHEWS). 



AB, a perpendicular rod descending fro.n a 

 universal joint, which is not shown in the figure ; 

 CD, a brass sheath, moving easily on the rod, and 

 bearing on its upper end an ivory pulley, and at 

 its lower end a horizontal bar, which is inter- 

 rupted by a plate of hard rubber, I. The per- 

 pendicular rod EF moves on the horizontal ba- 

 by the hinge-joint, J. EF is hooked at one end 

 for attachment to the heart, and bored at the 

 other for a thread which, passing over the pulley 

 at C, passes through the universal joint arid 

 moves a writing lever not shown in the figure. 

 CD is prevented from moving up AB by a ring of 

 brass, G, which is screwed to AB, but is not 

 attached to CD ; the hook F can therefore move 

 to and f'-om AB, and can rotate round it, whiK 

 it cannot move up or down. The hooks F and H 

 are insulated from each other by the hard rubber, I . 

 H is a binding post through which, and thro, gh 

 another connected with A, induction shocks 

 may be sent at will through the portion of the 

 heart lying between the hooks. 



now be no inhibition of 

 the heart. Incidentally 

 it may be seen that stimu- 

 lation of the central end 

 of the vago-sympathetic 

 causes strong, though, of 

 course, with opened chest, 

 abortive, respiratory 

 movements. 



(c) Pith a frog (brain 

 and cord), dissect out 

 the sciatic nerve on one 

 side up to the sacral 

 plexus. Cut off the whole 

 leg. Drop the cut end of 

 the nerve on the heart, 

 and hold the preparation 

 so that the nerve touches 

 the heart also by its longi- 

 tudinal surface. At each 

 cardiac beat the nerve 

 is stimulated by the ac- 

 tion current (Chap. XI.), 

 and the muscles of the 

 leg contract. 



(d) Raise the board so 

 that the head of the ani- 

 mal is down and the hind- 

 feet up, and note whether 

 there is any effect on the' 

 action and filling of the 

 heart. Repeat the ob- 

 servation with' head up 

 and feet down. 



(e) Compress the aorta 

 with the fingers, and 

 observe the effect on the 

 degree of dilatation of 

 the various cavities of 

 the heart. Repeat the 

 experiment with the in- 

 ferior vena cava, and 

 compare the results. 



(/) Smoke a drum. 

 Insert the hooks of the 

 myocardiograph (Fig. 83) 

 into the ventricle, taking 

 care not to penetrate 

 deeply into the wall. 

 Arrange the lever to write 

 on the drum. While a 

 tracing is being taken 

 stimulate the peripheral 

 end of the vagus. Un- 

 hook the cardiograph. 



(g) Stop the artificial 



