294 



PRACTICAL PHYSIOLOGY. 



[LXI. 



3. Dudgeon's Sphygmograph (fig. 216). 



Adjust the instrument on the radial artery by means of an 

 elastic strap, carefully regulating the pressure which can be gradu- 

 ated from 1-5 ounces by means of the milled head. Smoke 

 the band of paper, insert it between the rollers, and take a tracing. 

 Study the tracing (fig. 217). 



FlGf. 219. Ludwig's Support for Arm for the Sphygmograph. 



4. Ludwig's Sphygmograph. Use this instrument (fig. 218). 

 It is not unlike a Dudgeon's Sphygmograph, but there is a frame 

 adapted to the arm, and an arrangement for keeping the arm steady 

 while the hand grasps a handle for the purpose. 



By the device shown in fig. 219 the arm is kept quite steady 

 and always in the same position. In fact, we find it most con- 

 venient for taking tracings with either Dudgeon's or Ludwig's 

 Sphygmograph. It has also been found most valuable for clinical 

 work. It is made by Petzold of Leipzig. 



ADDITIONAL EXERCISES. 



5. Action of Amyl Nitrite. 



(a.) With the Sphygmograph adjusted, take a tracing, and then place two 

 drops not more of amyl nitrite on a handkerchief, and inhale the vapour. 



