174 



MEASUREMENT OF THE VELOCITY OF THE BLOOD-CURRENT. 



i. 



The velocity-curve (Fig. 69, III) is recorded by permitting smoked paper to 

 pass slowly before the tip of the indicator in the direction of its long axis. The 

 apparatus is of value because it registers the characteristic variations in the veloc- 

 ity of the blood-current that accompany each beat of the pulse. The dromographic 

 curve resembles a pulse-curve, and, like the latter, it possesses a primary (P), as 

 well as a secondary, recoil-elevation (R) . 



5. Cybulski s photoheniotachometer is constructed on the principle of Pitot's 

 tube. 



When fluid flows through a tube d e (Fig. 70, //) in the direction indicated by 

 the arrows, the column of fluid stands at a higher level in the manometer p than in 



the manometer m. While m y 

 indicates only the lateral pressure, 

 p x indicates the lateral pressure 

 and in addition the velocity-height 

 of the fluid. The velocity of the 

 current in the tube may then be de- 

 termined from the difference in the 

 two levels. Fluid may be per- 

 mitted empirically to pass through 

 the tube II d e with varying ve- 

 locity and the difference in level 

 between the two tubes p m that 

 corresponds to the different de- 

 grees of velocity at the current be 

 determined. 



The form of Pitot's tube em- 

 ployed by Cybulski is somewhat 

 different, being bent at a right 

 angle (/, c p}. The extremity c is 

 tied into the central, and the ex- 

 tremity p into the peripheral, por- 

 tion of the divided artery. When 

 the blood is allowed to flow freely, 

 the fluid rises to a higher level in 

 the manometer a, which lies in the 

 direction of the current, than in b. 

 In order to avoid excessive 

 length in the manometers a and b 

 and thus to render the apparatus 

 practically useful, Cybulski con- 

 nects the manometers a and b by a 

 tube shaped like a hairpin, which is 

 filled with air and can be closed by 

 means of a stopcock (i) applied 

 above the bend. The fluid is allowed 

 to rise to the points i and 2. If 

 the stopcock (i) is then closed, the 

 tubes represent an air-manometer 

 ,u f ba CybU ' Ski S j" ^ich the difference between the 

 levels i and 2 is sharply defined. 



As the surfaces of the columns 



of fluid i and 2 continually alter their position with respiration and pulse-beat, 

 that is, as the manometers record the respiratory and pulsatory variations in the 

 velocity of the fluid passing through the tube c p, the fluctuations of the two 

 levels may be advantageously photographed with a camera provided with a 

 rapidly moving background, K. 



Fig. C is a reproduction of the curves obtained from the carotid artery of the 

 dog. During the time represented by the interval between i l and i the velocity 

 was 238 mm.; in the phase between 2jand 2, 225 mm.; and, finally, between 3 t and 

 3,177 mm. The velocity is greatest at the end of inspiration and at the beginning 

 of expiration. Asphyxia at first increases the velocity. It is increased by paraly- 

 sis of the sympathetic and becomes smaller when the nerve is stimulated. Divi- 

 sion of the vagus increases the velocity, while stimulation of the nerve naturally 

 diminishes it. 



FI - 7 



