240 



EXPERIMENTAL PHYSIOLOGY. 



The steady fall of the blood-pressure represents the fall 

 obtained when the central end of the depressor nerve is 

 stimulated (the vagi being divided). 



(/.) Two sphygmographs may be 

 adjusted on the arterial tube, one 

 near the heart, and the other near 

 the capillaries, tracings being taken 

 and compared. 



(g.) The velocity of the pulse- 

 wave may be estimated as in Lesson 

 LIT., 1. 



4. The Rheometer (Fig. Ill) is used 

 to measure the amount of blood flowing 

 through a vessel in a given time. The 

 nozzles of the instrument are inserted 

 and tied into the artery of an animal, 

 but as the student is not permitted to 

 do this, use an india-rubber tube to 

 represent the artery. 



(a.) To represent the heart or 

 the weight of a column of fluid 

 arrange a Marriotte's flask or funnel 

 on a stand, and to the outflow tube 

 attach a narrow india-rubber tube, 

 and clamp it after filling it with 

 defibrinated blood. Suppose the 

 tube to represent an exposed artery, 

 clamp or apply and tighten two 

 ligatures, about an inch apart, 

 round the middle of the tube. Fill 

 one bulb of the instrument with 

 defibrinated blood and the other 

 with clear almond oil, and close 

 the top of the instrument with a 

 glass plug. 



Fig. Ill Rheometer. 



(6.) Divide the part of the tube 

 included between the two ligatures, 

 and tie into either end the nozzles 

 provided with the instrument. Call 



