IO6 PRACTICAL HISTOLOGY. [ll. 



LESSON II. 

 THE BLOOD. 



UNDER the microscope blood is seen to consist of a clear, transparent 

 fluid, the plasma or liquor sanguinis, in which are suspended the 

 blood-corpuscles. The blood-corpuscles are of two kinds, the red 

 or coloured, and the white, pale, or colourless. Besides these, 

 i-here fall to be examined the blood-plates, or, as they are also 

 sailed, blood-tablets or platelets. 



( Blood-plasma. 

 Blood \ ( Red. 



I Corpuscles < White. 



( Platelets. 



BLOOD-CORPUSCLES OF AMPHIBIANS. 



(A.) Coloured Corpuscles of Amphibians (Newt or Frog). After 

 destroying the brain of a newt or frog, a drop of blood may be 

 obtained from the cut end of the tail of the former, or from the cut 

 surface after amputation of the foot of the latter. 



1. Bed Corpuscles (H). Place a small drop of blood in the 

 centre of a perfectly clean slide and cover it at once with a cover- 

 glass. Examine it with a high power. To avoid the pressure of 

 the cover-glass, a short length of a hair may be placed in the blood 

 droplet before the cover-glass is applied. 



(a.) Observe the coloured and colourless corpuscles, the former 

 much more numerous than the latter (fig. 61). 



(b.) Study the red corpuscles. Observe that they are very numer- 

 ous, elliptical in outline when seen on the flat, slightly yellowish 

 in colour ; their border or contour is. even and well denned. Select 

 one seen on edge, and note that it is a thin ellipse, pointed at the 

 ends, becoming gradually thicker in the centre, so that it is a bi-convex 

 elliptical disc. Sometimes one corpuscle can be seen overlying a 

 subjacent one, in which case the outline of the latter can be dis- 

 tinctly seen through the former, indicating that the corpuscles are 

 transparent (fig. 61). Notice within each corpuscle a lighter oval, 

 central area, indicating the existence of an elliptical, colourless, 



