400 FOODS CIRCULATED AND USED IN THE BODY 



The lacteals. We have already learned that part of the digested 

 food (chiefly sugars, amino acids, salts, and water) is absorbed 



directly into the blood through the 

 walls of the villi and carried to the 

 liver. Fat, however, is passed into 

 the spaces in the central part of 

 the villus known as the lacteals. 

 This fluid or lymph then passes 

 from the lacteals into other lym- 

 phatics, and eventually drains into 

 the blood system by way of the 

 thoracic duct. Shortly after a 

 meal the lacteals are filled with a 

 white fatty substance, but at other 

 times they are filled with a fluid 

 very similar to the lymph in the 

 other lymphatics. 



Laboratory Exercise. What is the 

 effect of exercise on the heartbeat ? 



Place the middle finger of the right 

 hand two inches from the ball of the 

 thumb, to locate the pulse. Count the 

 number of beats per minute. The 

 normal rate in men is seventy-two 

 beats per minute ; in women, seventy- 

 six. It is higher in children. 



Then under the direction of a 

 leader, take a hard setting-up drill 

 for three minutes with the windows 

 open. Count the pulse beats as be- 

 fore and tabulate the result. Note 

 any difference in respiration. 



What effect did the exercise have 

 on the rate of the heartbeat? Can 

 you explain the reason? • Can you 

 explain the difference in the rate of 

 Diagram of the circulatory system. The respiration? Show in your table the 

 l^J^^^^h^JT'h^ difference between the normal pulse 



those containing venous blood are blue, . . , . . F 



and the lymphatics are yellow. and the one taken after exercising. 



The effect of exercise on the circulation. Exercise in modera- 

 tion is of undoubted value, because it sends more blood to parts 



