THE CIRCULATION OF THE BLOOD 519 



The frequency required to make the flow con- 

 tinuous is now much less than when the peri- 

 pheral resistance was low. 



THE RELATION BETWEEN RATE OF FLOW AND 

 WIDTH OF BED 



In a frog slightly paralyzed with curare destroy 

 the brain by pithing, with the least possible loss 

 of blood. Lay the frog back down on the mes- 

 entery board. Open the abdomen in the median 

 line. Draw the intestine over the cover glass 

 upon the cork ring so that the mesentery may 

 lie upon the glass evenly and without stretch- 

 ing. The mesentery must be kept constantly 

 moist with normal saline solution. Examine 

 the blood vessels in the mesentery with No. 3 

 Leitz Objective. 



Note the swift flow in the larger vessels and 

 the slow movement of the blood through the 

 capillaries. 



The combined cross-sections of the capillaries in 

 the body are vastly greater than the cross-section 

 of the arteries or the veins. The total quantity 

 of blood passing in a unit of time through the 

 arteries or veins and the capillaries is the same. 

 If less passed through the capillaries than through 

 the arteries, the capillaries would soon be gorged 



