CHAP. VII 



DIGESTION 



73 



changed. But pota- 

 toes, beefsteak, eggs, 

 bread, and, in fact, 

 all the solid food 

 materials must be 

 changed very much 

 before they can en- 

 ter the blood and be 

 of value to nourish 

 the cells. We shall 

 now find out how 

 the solid foods are 

 changed into blood. 

 65. The Alimen- 

 tary Canal. The 

 air reaches the blood 

 through a series of 

 organs called air 

 passages, and the 

 other foods enter 

 the body by means 

 of a series of organs 

 which together con- 

 stitute the alimentary 

 canal, or digestive 



tract. The alimen- Fir " 35- The alimentary canal (Zuppke). 



tary canal is a long tube that extends from the mouth 

 to the end of the large intestine. It is a canal through 

 the body, with enlargements at certain places. This 

 tube consists of the mouth with the teeth and tongue, 



