ABSORPTION 117 



QUESTIONS ON LESSON XX. 



1. What is meant by absorption ? What are the organs concerned in the 



absorption of nutriment ? 



2. Where does the absorption of nutritious matter commence ? In what parts 



is it continued ? 



3. How does the absorption by blood-vessels differ from that by the lacteals ? 



4. What are lacteals and lymphatics ? 



5. Describe the structure of a villus. In what way is it particularly adapted 



for absorption ? 



6. What are the organs and vessels which make up the lymphatic system ? 



7. What is the difference between lymph and chyle ? 



8. How is the food conveyed from the alimentary canal into the blood ? 



9. What is the thoracic duct ? Where is it situated ? What does it contain 



during fasting, and what shortly after a meal ? 

 10. What are lymphatic glands ? What is their use ? 



LESSON XXI. 

 THE BLOOD. 



THE blood consists of a colourless alkaline fluid called the 

 liquor sanguints, and myriads of minute floating bodies called 

 corpuscles. 



The liquor sanguinis (Lat. sanguis, blood), called also the 

 plasma, consists of water in which is dissolved certain mineral salts 

 and albumen and other nitrogenous matter. 



The blood corpuscles are of two kinds, usually termed the red 

 and the white or colourless 



The red corpuscles are minute circular discs, concave on both 

 sides, having a diameter of about ^uVry inch, and a thickness of 

 about rwrnr i ncn - If placed flat, edge to edge, ten millions of 

 (hem would be required to cover a square inch. They are so 

 numerous in the blood that they make it a thickish liquid, and 

 probably form about forty per cent, of the total weight of the blood. 

 When examined singly under a powerful microscope they are not 

 red, but of a pale yellowish colour ; yet these are the bodies 

 which, when seen en masse, give to the blood its uniform red colour. 

 These corpuscles seem to be supported by a firm elastic framework, 

 so that they readily change their shape in passing through narrow 

 apertures, and regain it immediately after. 



The white or colourless corpuscles are a little larger than the 

 red, being about ^Vrr mcn m diameter. Being composed of a 

 very soft, jelly-like substance (protoplasm} they readily change 

 their form. They much resemble a minute animal organism, 



