106 



BOYS AND GIRLS IN BIOLOGY. 



with air. It was afterward found out that they carried 

 the blood from the heart. These arteries carry the 

 blood over all the body, and they get smaller and small- 



Fig, 100. 



Hair-Tubes, or Capillaries. 



The Circle which the Blood makes going from and to the Heart.— The 

 Light Lines stand for the Pure Blood, and the Dark for the Impure. 



er until they end in very tiny vessels called capillaries, 

 because they are so fine — even finer than hairs. You 

 may not know it, but every hair on your head is a hol- 

 low tube. As the blood passes through these hair-like 



