202 ELEMENTARY BIOLOGY. [XIII. 



corpuscles in the capillaries from pressure, &c.; 

 their elasticity as indicated by the readiness with 

 which they recover their shape when the cause 

 of distortion is removed; the way the white cor- 

 puscles creep along, with a tendency to stick 

 to the capillary wall. 



4. Examine a drop of frog's blood with the microscope 

 (^ or ^ obj.). Sufficient blood to supply a whole 

 class for this purpose can be obtained by killing 

 one frog and opening its heart. 



It consists of solid bodies {corpuscles) floating 

 in fluid {plasma). 



a. The red corpuscles. 



a. Their form: oval when seen in front face; 

 almost linear in profile but slightly swollen at 

 the centre. 



/3. Their size: their length, breadth, and thick- 

 ness; measure, 



7. Their colour : pale yellow, when seen individu- 

 ally ; redder if a thick mass of them is looked 

 at. 



S. Their structure : they are homogeneous for the 

 most part, but possess a round granular central 

 nucleus. 



e Treat with water ; they swell up and] become 

 more spherical ; their colouring matter is gra- 

 dually discharged ; the nucleus is rendered very 

 evident, and ultimately all the rest of the 

 corpuscle disappears. 



5". Treat with dilute acetic acid ; results game as 

 with water, but produced more rapidly. 



