THE USE OF FOOD 375 



to the bones which act as (5) Bones also (6) delicate 



organs such as the (7) and spinal (8) Bones are made 



of (9) as well as (10) matter. Muscles which cause 



movement are found in (11) : one (12) when its opposite 



relaxes. Tendons (13) muscles to bones; (14) bind 



bones together. Between bones which move against each other 



are found (15) of elastic (16) which save the body from 



unnecessary jars. Good standing posture is brought about by 



having the head and shoulders (17) over the center of (18) 



of the body. 



STORY TEST 



JACK WRITES ABOUT POSTURE 

 Read carefully and critically. List all the errors and suggest corrections. 



Anyone who hopes to succeed in life needs good posture. Not 

 only do employers like to see it in people who come to them for 

 jobs, but it helps one keep well. Good posture can never become 

 a matter of habit, you always have to practice it consciously. 

 Postural exercises do not do us much good because if you practice 

 them you get tired and that is bad. Fallen arches are a symptom 

 of bad posture. You can test your arches by walking with wet 

 bare feet on a flat surface. A wide mark made on the paper 

 between toe and heel shows that the arch is perfect. Girls often 

 wear shoes with high heels, which tip the body forward. This is 

 often a cause of poor posture. 



PROBLEM IV. HOW DOES THE HUMAN MACHINE 

 MAKE USE OF FOOD? 



The Problem of Getting Food Where It Can Be Used. 



If we recall our auto, we remember that fuel is burned in 

 the cylinders. The explosion of gas pushes the piston, 

 which causes the shaft to revolve. This transmits power 

 to the wheels and the car moves. Very different condi- 

 tions exist, however, in the human machine. Food is not 

 oxidized where it is taken into the body, but in the individ- 

 ual cells which do the work. If this is true, then while you 

 are reading these words, work is done and food is oxidized 

 in your hands, which hold the book, in the muscle cells 

 which move your eyes, in the cells in the eye which register 



