290 THE CIRCULATION IN THE BLOOD-VESSELS. [CH. xxi. 



with the manometer, and the pressure got up by the use of a 

 syringe (which is seen in fig. 279 g\ before the clip is removed from 

 the artery. The manometer itself is a hollow C-shaped spring 

 filled with liquid ; this opens with increase, and closes with 

 decrease of pressure, and the movements of the spring are 

 communicated to a lever provided with a writing point. 



Fig. 279. Fick's Kymograph, improved by Hering (after McKendrick). a, hollow spring 

 filled with alcohol, bearing lever arrangement 6, d, c, to which is attached the marker 

 e. ; the rod c passes downwards into the tube /, containing castor oil, which offers 

 resistance to the oscillations of c ; g, syringe for filling the leaden tube h with saturated 

 sulphate of sodium solution, and to apply sufficient pressure as to prevent the blood 

 from passing into the tube Ji at j, the cannula inserted into the vessel ; I, abscissa- 

 marker, which can be applied to the moving surface by turning the screw TO ; k, screw 

 for adjusting the whole apparatus to the moving surface ; o, screw for elevating or 

 depressing the Kymograph by a rack-and-pinion movement ; n, screw for adjusting the 

 position of the tube/. 



Hiirthle's manometer (see p. 243) is also very much used. The 

 advantage of these forms of manometer is that the character of 

 each individual movement is much better seen ; in the case of a 

 heavy liquid like mercury the inertia is so great that it cannot 

 catch the finer movements which we have seen as secondary 

 vibrations on the pulse wave. If Fick's or Hiirthle's manometer 



