82 



ACTION OF FLUIDS ON THE HEART. 



by the fact that the heart beats rhythmically when it contains no blood. Blood 

 and other fluids which are supplied to an excised heart are not the cause of its 

 rhythmical movements, but only the conditions on which these movements depend. 

 [Methods The studv of the action of fluids upon the excised frog's heart has been rendered 

 possible by the invention of Ludwig's "frog-manometer." The apparatus (fig 60) consists 



of (1) a double-way cannula, c, which is tied into the 

 heart, h ; (2) a manometer, m, connected with c, and 

 registering the movements of its mercury on a revolving 

 cylinder, cyl ; (3) two Mariotte's flasks, a and b, which 

 are connected with the other limb of the cannula. 

 Either a or b can be placed in communication with the 

 interior of the heart by means of the stop-cock, s. The 

 fluid in one graduated tube may be poisoned, and the 

 other not; d is a glass vessel for fluid, in which the 

 heart pulsates, e' and e are electrodes, e is inserted into 

 the fluid in d, e' is attached to the German silver cannula 

 which is shown in fig. 61.] 



[In the tonometer of Roy (fig. 62) the ventricle, h, 

 or the whole heart, is placed in an air-tight chamber, o, 

 filled with oil. As before, a "perfusion" cannula is 

 tied into the heart. A piston, p, works up and down in 

 a cylinder, and is adjusted by means of a thin flexible 

 animal membrane, such as is used by perfumers. 

 Attached to the piston by means of a thread is a 

 writing-lever, I, which records the variations of pres- 

 sure within the chamber, o. When the ventricle con- 

 tracts, it becomes smaller, diminishes the pressure within 

 o, and hence the piston and lever rise ; conversely, when 

 the heart dilates, the lever and piston descend. Varia- 

 tions in the volume of the ventricle may be registered, 

 without in any way interfering with the flow of fluids 

 through it.] 



[Two preparations of the frog's heart have been used 

 (1) The "heart," in which case the cannula is intro- 

 duced into the heart through the sinus venosus, and 

 a ligature is tied over it around the auricle, i.e., above the auriculo-ventricular groove. Thus 

 the auriculo-ventricular ganglia and other nervous structures remain in the preparation. This 



was the heart preparation em- 

 ployed by Luciani and Rossbach. 

 (2) In the "heart-apex" or 

 apex preparation, the cannula 

 is introduced as before, but the 

 ligature is tied on it over the 

 ventricle, several millimetres 

 below the auriculo-ventricular 

 groove, so that this preparation 

 contains none of the auriculo- 

 ventricular ganglia, and, accord- 

 ing to the usual statement, this 

 part of the heart is devoid of 

 nerve ganglia. This is the pre- 

 paration which was used by 

 Bowditch, Kronecker and Stir- 

 ling, Merunowicz, and others. 



I 



Fig. 60. 

 Scheme of a frog-manometer, a, b, 

 Mariotte's flasks for the nutrient 

 fluids ; s, stop-cock ; c, cannula ; m, 

 manometer ; h, heart ; d, glass cup 

 for h ; c', e, electrodes ; cyl, revolving 

 cvlinder. 



Fig. 61. 

 Perfusion cannula for a frog's 

 heart, c, for fixing an electrode ; 

 t/, the heart is tied over the 

 flanges, f>re venting it from 

 slippiug out ; e, section of d. 



Fig. 62. 

 Roy's heart tonometer, h, heart ; o, air-tight chamber ; 

 p, piston ; I, writing-lever ; e, outflow tube. 



The first effect of the application of the ligature in both cases is, that both preparations cease to 

 beat, but the " heart" usually resumes its rhythmical contractions within several minutes, while 

 the " heart-apex" does not contract spontaneously until after a much longer time (10 to 90 mins.).] 

 [If the "heart-apex " be filled with a 6 per cent, solution of common salt, the contractions 

 are at first of greater extent, but they afterwards cease, and the preparation passes into a con- 



