I20 SCIENCE PRIMERS, [§ vii. 



minute particles into which the bile and pancreatic 

 juice have divided the fat taken as food. We know 

 this because when no fat is eaten the lacteals do not 

 get milky ; and when for any reason bile and pancre- 

 atic juice are prevented from getting into the intes- 

 tine, though ever so much fat be eaten, it does not 

 get into the lacteals at all, it remains in the intestine 

 in great pieces, and is finally cast out as useless. 



52. This, then, is what becomes of the food-stuffs : — 



The fats are broken up by the bile and pancreatic 

 juice into minute particles. These minute particles, we 

 do not exactly know how, pass through the epitheUum 

 of the villus into the lacteal vessels, from the lac- 

 teals into the thoracic duct, and from the thoracic 

 duct into the vena cava. Thus the fats we eat get 

 into the blood. 



The starch is changed into sugar in the mouth by 

 saliva, and in the intestine by the pancreatic juice ; 

 but sugar passes readily through membranes, and so 

 slips into the blood capillaries of the walls of the 

 alimentary canal. Thus all the sugar we eat, and 

 all the goodness of the starch we eat, pass into 

 the blood. 



The proteids are dissolved in the stomach by the 

 gastric juice, and what passes the stomach is dis- 

 solved in the intestine, dissolved in such a way that 

 it can pass through membranes; and thus proteids 

 pass into the blood. 



Probably some of the sugar and proteids pass into 

 the lacteals as well. % 



The minerals are dissolved either in the mouth, 

 or :n the stomach, or in the intestine, and pass into 

 the blood. 



