86 



ELEMENTARY PHYSIOLOGY. XVI. 



From A and V, representing a main artery and vein 

 respectively, tubes run to mercury manometers, M a9 

 M v , by which the pressure in these can be recorded on 

 a revolving drum. Levers are placed on the * arterial 

 tube, at L l and L 2 , by which the passage of the pulse- 

 wave can be recorded. A recording tambour, R.T., is 

 connected with the vessel PL by which variations in 

 volume of the arterial tube in the vessel can be recorded; 

 the vessel P thus represents a plethysmograph. 



Fig. 25. 



On the course from the arterial tube to the venous 

 tube is a tube e supplied with a tap, T, the opening of 

 which causes changes in arterial and venous pressure 

 corresponding to those caused by dilatation of small 

 arteries and capillaries, x and y are tubes by which 

 the effect of opening the arteries and veins can be 

 observed. 



All the shaded parts are of metal, the capillary tubes 

 are of glass, both are connected with the rest of the sys- 

 tem by india-rubber tubing, that leading to the mano- 

 meters being thick- walled (pressure tubing). In order 



