IX 



CARDIAC MUSCLE AND NERVES 



289 



right auricle and the ventricle of the frog. No artificial valves are required 

 to separate the vessel containing the nutrient solution from the tonographic 

 apparatus, since the auriculo-ventricular valves of the heart itself are utilised 

 for the purpose. As shown in Fig. 124, the heart is attached to two cannulae, 

 one of which is tied to the aorta so that the valve is unable to perform its 

 function, the other to the sinus. The two cannulae communicate on the one 

 hand with the vessel containing the serum or nutritive solution, on the other 

 with two separate elastic tomographs similar to small Marey's capsules, which 

 record the oscillations of pressure, in the right auricle and ventricle as tran.- 

 mitted by the air. When disconnected from the reservoir by applying a 

 couple of pressure forceps at the 



points indicated in the figure, A B C 



the heart is made to beat in 

 presence of a small quantity of 

 fluid which circulates continu- 

 ously. When, on the other 

 hand, the forceps are undamped, 

 so as to open communication 

 with the reservoir, the whole 

 of the fluid present is perfused 

 through the heart. In the first n 

 case the curves recorded by the 

 two tonographs are naturally 

 more ample, because they repre- 

 sent the total pressure developed 

 within the heart ; in the second 

 case they are less ample, because 

 the lateral pressure is recorded. 



(b) Plethysmographic Method*. 

 These aim at recording the 



variations in the volume of the 

 heart during the pulsatory cycle. 

 They have been applied in vari- 

 ous ways to the heart of the frog 

 or the tortoise, by Francois- 

 Franck, Roy, Gaskell, and 

 Williams. As shown in Fig. 

 123, plethysmograms of the 

 frog's heart are most simply 

 obtained by a slight modifica- 

 tion in Williams' apparatus, the 

 heart being placed in a small 

 closed cylinder empty or filled 

 tympanum. 



(c) Mijmjraphic or Gardiographic Methods. By these we can record the, 

 modifications in the external form of the heart, produced by cardiac systole 

 or diastole. These methods have been applied in a variety of ways. Alight 

 lever may be placed directly upon the ventricle, or two levers, one on the 

 ventricle, the other on the auricles, when the magnified movements due to 

 changes in form of the heart (Marey's double myograph for heart of frog and 

 tortoise) can be read oft'. An ingenious modification of this method is repre- 

 sented in Fig. 125 (Marey's pinee myoyraphique). Gaskell introduced a 

 method of suspension with which he obtained interesting results. It con- 

 sisted in fixing the heart at the auriculo-ventricular groove by a screw-clamp, 

 which could be easily adjusted. The apex of the ventricle and tip of the 

 auricle are attached by silk threads to very light levers, placed respectively 

 above and below the heart, which are pulled upward or downward during 

 systole, and record the magnified movement on a revolving cylinder. 



VOL. I TJ 



Kic. 1-2-2. A, Simple cannula (Lucuuii) for frog's heart, 

 natural size. Consists of glass tube , joined to rubber 

 tube 6, which connects it with the manometer, and 

 has various metal rings (c) at the end, 2 mm. apart, 

 by which ligatures can be applied to the heart at 

 equal distances. B, Two-way cannula (Kronecker) 

 composed entirely of metal divided into two arms, 

 c, b, which unite externally into one arm il, divided 

 internally by a septum as shown in section at e. The 

 arm is connected with the chamber for the serum ; 

 the arm li with the recording manometer. The metal 

 wire c serves as electrode, in the electrical stimula- 

 tion of the heart. The fluid expelled by the heart 

 at each systole is partially turned out, so that fresh 

 serum enters the heart at each diastole. C, Cannula 

 adopted in Williams' apparatus. The same two- 

 way cannula, as above, with the addition of a small, 

 simple metal cannula /<, which is introduced into 

 the ventricle by the bulbua aortae. 



with oil, and connected with a Marev's 



