236 



PHYSIOLOGICAL PHYSICS. [Chap. xxi. 



method of studying and registering movements of the 

 heart under varying conditions. 



The frog-heart apparatus of Ludwig and 

 pupils affords a most valuable and interesting means 

 of studying the heart, a means not very widely known 

 in this country. The apparatus is shown in Fig. 114. 



It consists of two tubes (1 and 2) 

 similar to the burettes used for 

 quantitative chemical analysis, and 

 marked off into tenths of a cubic 

 centimetre. They communicate 

 with one outlet, guarded by a two- 

 way stop- cock. The tubes are 

 supported on a stand, and in the 

 same frame is held a small 

 mercury manometer m, one limb 

 of which is turned and pro- 

 longed downwards, so that it opens 

 at the same level as the burette 

 outlet. A branch of the same 

 limb is also prolonged upwards 

 and backwards and is guarded with a stop-cock. The 

 limb m contains a fine stem of glass floating in the 

 mercury by a bulbous extremity, the projecting end 

 being bent at right angles and terminating in a point 

 s for writing on a blackened revolving cylinder. For 

 fixing the frog heart to the apparatus, the Kronecker 

 heart canule, shown in the upper part of the figure, 

 is used. It is divided into two compartments, one 

 communicating with the branch A, and the other with 

 the branch B. To each of the branches is attached a 

 short piece of caoutchouc tubing. A frog having been 

 pithed and its spinal cord destroyed, the thorax is 

 opened and the heart exposed. The pericardium is 

 opened in front, the heart turned over, and a very fine 

 vessel passing from the pericardium to the back of the 

 heart ligatured. The sinus venosus is now opened by 



Fig. 114. Frog-heart 

 Apparatus. 



