RATE OF MOVEMENT OF THE BLOOD 



207 



shape of the letter U (Fig. 61 No. 1), or by merely allowing the vessel to 

 bleed into a graduated tube and seeing how long the blood column takes 

 to travel from one end to the other. This method is of considerable 

 value in measuring the velocity of flow from small vessels such as the 

 veins coming from glands and muscles. For larger vessels a so-called 

 stromuhr is employed. There are numerous forms of stromuhr; that 

 shown in the diagram (Ludwig's) (Fig. 61 No. 2) consists of two glass 

 bulbs united above, and connected below with tubes that open flush with 

 the surface of a circular platform of brass. This is pivoted at its center 

 with another similar platform also having flush with the surface the open- 

 ings of two tubes which are connected below with the cut ends of the 

 artery or vein. In a certain position of the upper platform, the tubes' 

 from the artery or vein are exactly opposite those of the bulbs, so that the 



Fig. 61. Forms of apparatus for measurement of blood velocities. 



/. Volkman-n's hemodromometer. The blood vessel is attached to the two short side tubes, 

 and according to the position of the stopcock, the blood flows either directly between them or 

 through the U-shaped glass tube. 



2. Ludwig's stromuhr. The tubes on the lower end of each of the two glass bulbs pierce 

 a circular brass platform and end flush with its surface. This platform pivots at its center on 

 a similar lower platform with two openings connected with the tubes that lead to the blood 

 vessel. 



blood can flow through the bulbs from the one end of the blood vessel to 

 the other. To use the instrument the proximal bulb is filled with oil and 

 the peripheral one with physiological saline. The clip is then removed 

 from the artery or vein and the blood flows in and displaces the oil, which 

 in turn displaces the saline into the peripheral end of the blood vessel. 

 When the blood has risen to a mark on the tube joining the two bulbs, the 

 instrument is rapidly rotated so that the oil is brought back again into the 

 proximal position, the rotation being effected so quickly that there is no 

 distinct interruption in bloodflow. The operation is repeated in this way 

 for a given period of time. Counting accurately the number of revolu- 

 tions, then multiplying the number of revolutions by the capacity of the 



