CH. X\T.] THE KYMOGRAPH. 287 



clotting. Before the clip is removed from the artery, the pressure 

 is first got up by a syringe (or pressure bottle containing the 

 same saline solution suspended at a good height above the 

 apparatus and connected to it by a tube), so that the mercury 

 rises in the distal limb to a height greater than that of the 

 anticipated blood-pressure ; this prevents blood passing into the 

 canuula when the arterial clip is removed. 



In the distal limb of the U-tube, floating on the surface of the 

 mercury, is an ivory float, from which a long steel wire extends 



Fig. 275. The Manometer of Ltidwig's Kymograph. It is also shown in fig. 276, i>, c, K. 

 The mercury which partially fills the tube supports a float in the form of a piston . nearly 

 filling the tube ; a wire is fixed to the float, and the writing style or pen fixed to the 

 wire is guided by pawing through the brans cap of the tube : the pressure is communi- 

 cated to the mercury by means of a flexible metal tube filled with fluid. 



upwards, and terminates in a writing point. The writing point 

 may be a stiff piece of parchment or a bristle which writes on a 

 moving surface covered with smoked paper, or a small brush 

 kept full of ink which writes on a long strip of white paper 

 made to travel by clockwork in front of it. When the two limbs 

 of the mercury are at rest, the writing point inscribes a base line or 

 abscissa on the travelling surface ; when the pressure is got up by 

 the syringe it writes a line at a higher level. When the arterial 

 clip is removed it writes waves as shown in the diagram (fig. 274), 

 the large waves corresponding to respiration (the rise of pressure 

 in most animals accompanying inspiration),* the smaller ones to the 



The explanation of the respiratory curves on the tracing is postponed 

 till after we have studied Respiration. 



