CHAPTER XIX 



METHODS OP INVESTIGATING THE CIRCULATION IN THE 



BLOOD-VESSELS 



THE chief methods used can be practised upon a long india-rubber tube 

 through which water is pumped from a low reservoir by a Higginson 

 syringe actuated by some form of motor. After passing through the 

 system the fluid is again delivered into the reservoir (which represents 

 the capillary and venous systems). A mercury kymograph (fig. 64) 

 and other manometers such as Fick's C-spring (fig. 65), Hiirthle's 

 tambour (fig. 66), as well as the stromuhr (fig. 69) and other 

 instruments for measuring or estimating velocity, are connected 

 by means of T-tubes with the main india-rubber tube. The 

 use of each instrument is to be studied separately, the others being 

 temporarily shut off by screw clips. Notice how the movement 

 of any of the recording manometers may be damped by partially 

 closing the tube connecting it with the main system. Observe 

 the effect upon the pressure within the system (1) of increasing either 

 the rate of the pump or the amount delivered at each stroke ; (2) of 

 diminishing or enlarging the outflow from the main tube by a screw- 

 clip. This is equivalent to contraction or dilatation of the arterioles. 

 Take a tracing with each form of manometer. Also record the amount 

 of fluid passing through the stromuhr in one minute. Measure the 

 diameter of the artery in whose course the instrument is inserted, 

 and calculate from these data the velocity of flow. 



A dog's or lamb's kidney enclosed in a plethysmograph (such as is shown in 

 fig. 68) may also be connected laterally with the main system, and Ringer's 

 fluid allowed to flow in by the renal artery and out by the renal vein ; from 

 this it must be conducted straight to the reservoir. 



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