94 



ELEMENTARY PHYSIOLOGY. XVII. 



Compare the pressure with that obtained by method a. 



After use, press the end of the gauge on blotting 

 paper, dip it into distilled water, and press it again on 

 blotting paper. 



Fig. 27. 



6. The details of construction of Marey's and of 

 Dudgeon's sphygmograph will be demonstrated. Fasten 

 one of these on the wrist as the receiving tambour was 

 fastened in 2, and take a pulse tracing. 



7. Vascular dilatation and in consequence a fall of blood pressure 

 and an increase in the dicrotic wave may be observed by inhaling 

 a little amyl nitrite. A few drops are placed on a cloth or piece 

 of cotton wool, and inhaled once. If no effect is felt, it is inhaled 

 again, but cautiously, since excess causes dizziness and may cause 

 fainting. Observations may be made with the sphygmomanometer 

 and with the sphygmograph. 



