BY DR. BURDON-S ANDERSON. 219 



so the notion of the kymograph is said to have been suggested 

 by a contrivance of Watt's for registering the pressure of the 

 steam-engine. 



The principle of the kymograph consists in causing a pen, 

 fixed horizontally at the upper end of a vertical rod, the lower 

 end of which rests by a floating piston on the surface of the 

 mercurial column in the distal open limb of the manometer, to 

 write the up and down movements of the column on a surface 

 of paper progressing horizontally at a uniform rate by clock- 

 work. Since the time that Ludwig first employed it, the con- 

 trivance has developed into a method now commonly known as 

 the graphic method. 



Description of the Kymograph and Accessory Ap- 

 paratus now used in the Laboratory of University 

 College. 1 1. The arterial capula is a T-shaped tube of glass, 

 of the size and form shown in fig. 193, c. By its stem it is con- 

 nected with the manometer; one branch is drawn out and 

 bevelled, the other is of the same size as the stem, and when in 

 use is fitted with a short bit of caoutchouc tubing, guarded by 

 a steel clip. 



The canulated end is made as follows : The tube which it is 

 intended to use for the purpose is first softened in the flame of 

 the gas blow-pipe, and drawn out gently at the softened part. 

 It is then allowed to cool, and again heated in a pointed flam, 

 at x, and drawn out so as to make it assume the form 193, b. 

 It is then scratched with a sharp three-cornered file opposite 

 a:, and sundered by drawing the one end of the tube from the 

 other in the direction of its axis. The last step in the process 

 consists in filing off the cut end in the direction of the dotted 

 line, and smoothing the edges by touching them with the 

 border of an ordinary gas flame. A tube of this kind can be 

 inserted with great ease into an artery of considerably less 

 diameter than itself. Canulae of glass are always to be pre- 

 ferred to those of silver, not merely on the ground of facility 

 of introduction, but because a glass surface is much less apt 

 than one of metal to determine coagulation of the blood which 

 comes into contact with it. 



2. The stem of the arterial canula communicates with the 

 proximal arm of the manometer (see fig. 202) by a tube (f), of 

 which the part next the canula only is of India-rubber. The 

 rest is of lead; the purpose of the arrangement being to avoid 

 a certain modification of effect due to the yielding of the wall 

 of the tube, which becomes appreciable if the whole connector 

 is elastic. 



1 This instrument was made for me by Mr. Hawksley, of Blenheim 

 Street, and has advantages over any other form with which I am 

 acquainted. 



