44 PHYSIOLOGY FOE THE LABORATORY. 



II. THE NORMAL FLOWING OF THE BLOOD. 



Material. Water, which may be slightly colored red if preferred. 

 Apparatus. A small force-pump. Two wooden pails. 

 660 c.m. pure rubber tubing, 12 m.m. in diameter. 

 \% m. " " 6 m.m. 



560 c.m. " 5 m.m. " 



Three-way glass connecting tubing, F-shape. Six large size, 



12 m.m. in diameter, length of one arm 90 m.m. 

 Eight medium size, 6 m.m. in diameter, length of one arm 



65 m.m. 

 Two medium size, !T-shape tubing, 6 m.m. in diameter, length 



of one arm 65 m.m. 

 Sixteen small size, 4 m.m. in diameter, length of one arm 



60 m.m. 



64 c.m. glass tubing 12 m.m. in diameter. 

 192 c.m. " " 4 m.m. " 

 Two pinch-cocks. 

 35 c.m. of glass rod 2 m.m. in diameter, or pieces of a fine 



sponge. 



By means of an apparatus made of glass and rubber 

 tubing, the principal phenomena of the circulation of the 

 blood may be demonstrated. A small force-pump con- 

 nected with one end of the apparatus represents the action 

 of the heart. The large rubber tubing of one half of the 

 apparatus represents the arteries, and of the other half the 

 veins. The small passages in the sponge within the small 

 tubing, between the two parts, represent the capillaries 

 and cause the peripheral resistance. The difference in 

 structure between the arteries and the veins may be more 

 clearly shown, if the arteries are made of very elastic pure 

 rubber tubing, and the veins made of less elastic tubing 

 which has some linen fibres in its walls. The outlet at H 



