276 



THE CIRCULATION IN THE BLOOD-VESSELS [CH. XXII. 



larger waves to respiration, only the respiratory rise in pressure now 

 accompanies expiration. 



The capillary pressure is estimated by the amount of pressure 

 necessary to blanch the skin ; this has been done in animals and men 

 (v. Kries, Roy and Brown). 



Other manometers are often employed instead of the mercurial 

 one. Fick's is one of these. The blood-vessel is connected as before 

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



FIG. 244. Fick's Kymograph, improved by Bering (after M'Kendrick). a, Hollow spring tilled with 

 alcohol, bearing lever arrangement b, 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 h at i, the cannula inserted 

 into the vessel; I, abscissa-marker, which can be applied to the moving surface by turning the 

 screw m ; 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/. 



(which is seen in fig. 244, 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 pro- 

 vided with a writing-point. 



Hurthle's manometer (see p. 242) is also very much used. The 

 advantage of these forms of manometer is that the character and 

 extent of each pressure change is much better seen. In a mercury 



