THE BLOOD FLOW 



395 



bring the bulbs successively into communication with the cannula inserted in 

 the central end of the artery (C). To begin with, one of the bulbs is filled 

 with normal saline solution and the other with oil. The latter is first turned 

 toward the inflow tube (C). On permitting the blood to flow into this instrument 

 by removing the clip temporarily placed upon the central end of the artery, the 

 oil is forced upward and through the con- 

 necting tube into the limb containing the 

 saline solution. When the latter has been 

 completely driven into the peripheral end 

 of the artery, the bulbs are quickly re- 

 versed so that the oil is again brought 

 into direct communication with the influx, 

 while the blood is forced into distant ar- 

 terial channels. In order to obtain the 

 volume of the blood stream it is necessary 

 to record the number of revolutions of 

 the stromuhr in conjunction with the 

 time. Thus, if the capacity of the bulb 

 is 5 c.c. and it has been filled 12 times in 

 the course of one minute, then 60 c.c. of 

 blood have passed this point of the artery 

 in the course of this period. 



Much more serviceable instruments 

 for the calibration of the blood stream 

 have been devised by Hiirthle^ and Bur- 

 ton-Opitz.2 Both types of instruments 

 contain a piston which moves within a 

 cylinder and records its excursions upon 

 the paper of a kymograph. For this 

 reason, they are known as recording stro- 

 muhrs. The cylinder of the instrument 

 described by Burton-Opitz is adjusted 

 horizontally at the level of the blood- 

 vessel, while the resistance of the piston is 

 minimized by counterpoising (Fig. 208). 

 By means of a double U-shaped valve 

 with which the central and peripheral 

 segments of the blood-vessel are con- 

 nected, the blood may be diverted either 

 into the compartment to the left or to 

 the right of the piston. The piston is 

 thus forced to move successively from 

 left to right, and from right to left, its 

 movements being recorded upon the kymo- 

 graph by means of a lever and connecting 

 string. This instrument having been 

 properly calibrated, the quantity of blood 

 which has traversed it may be read off 

 directly from the paper. Naturally, the 

 insertion of the stromuhr necessitates a 

 temporary interruption of the blood flow 

 in this vessel, but unless unduly prolonged, 

 normal conditions are generally reestablished within a few moments after the re- 

 moval of the clips. As the instrument is filled with normal saline solution, and as 



.1 Pfliiger's Archiv, xcvii, 1903, 193. 



2 Ibid., cxxi, 1908, 150. Ishikawa and Starling have described a current 

 measurer of which a siphon forms the essential part. 



Fig. 207. — Ludwig's Stromuhr. 



a, Is filled with oil to tRe mark (c.c), 

 while b and the neck are filled with salt 

 solution or defibrinated blood; p, the 

 movable plate by means of which the 

 bulbs may be turned through 180 de- 

 grees; cc, for the cannulas inserted into 

 the artery; s, the thumb screw for turn- 

 ing the bulbs; h, the holder. When in 

 place the clamps on the arteries are re- 

 moved, blood flows through c into a, 

 driving out the oil arid forcing the salt 

 solution in b into the head end of the 

 artery through c'. When the blood en- 

 tering o reaches the mark, the bulbs are 

 turned through 180 degrees so that b lies 

 over c. The blood flows into b and 

 drives the oil back into a. When it just 

 fills this bulb, they are again rotated 

 through 180 degrees, and so on. (Howell.) 



