Fia. 137. — Ludwiff and Coats' Frog-heart Apparatus. 



A is a reservoir for serum, b, a stopcock to regulate the supply to the heart. 

 C, a piece of caoutchouc tubing connecting a and D. d, a glass cannula in the 

 vena cava inferior, d', another in the aorta. E, a manometer, f, a piece of 

 tubing closed by a clip, to allow of the escape of serum. Q, a fine pen, floating 

 on the mercury in e. h, the frog's heart. J, a sealed glass tube, passed through 

 the oesophagus k, and firmly held by a holder L. m, a nut which allows l to be 

 moved up and down, n, a second holder to support A. p, a stand witli upright 

 rod. s, a flap of skin to cover the heart and prevent drying, y, the vagus. 



