ADVANCED EXPERIMENTAL PHYSIOLOGY 



173 



renal vein stops the secretion of urine. After a temporary obstruction 

 albuminous urine is secreted. Half a grain of citrate of caffeine injected 

 intravenously will produce a fall of arterial pressure and a preliminary 

 contraction of the kidney, followed by expansion and increased flow 

 of urine. Observe the effect of extract of pituitary gland. This is the 

 most active diuretic known (Schafer). 



Plethysmography of the Arm. The arm is placed in the rubber 

 gauntlet of the plethysmograph. The plethysmograph is connected 

 with a recording tambour, a J_-piece being interposed. Record the 

 volume curve on a moderately fast drum. The tracing shows pulse 

 waves and respiratory oscillations. 



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FIG. 175. Limb plethysmograph. 



Fasten the armlet of the sphygmometer round the upper arm 

 and record the curve of venous congestion which results from raising 

 the pressure in the armlet. Repeat this ; after exertion the curve 

 rises much more steeply. This is a good comparative method of 

 studying the velocity of blood flow into man. 



