PRACTICAL PHYSIOLOGY 69 



into the vessels by gravitation. Make a cut into 

 the sinus venosus so that the Ringer's fluid may 

 flow freely out after it has traversed the blood-ves- 

 sels of the body ; the escaping fluid will drop from 

 the toes. Count the number of drops per minute, 

 and repeat the counting two or three times ; it will 

 be found that the flow is fairly regular. 



To test the effect of drugs upon the muscular 

 tissue of the arterioles the drug to be tested is 

 added in known quantity to the circulating fluid, 

 and by again counting the number of drops per 

 minute it can be determined whether the arterioles 

 are becoming dilated or contracted as the effect of 

 the drug. This experiment may be tried with a 

 decoction of suprarenal capsule. 



