Chap. II.) 



BLOOD. 



The elements of the blood described by Dr. Richard 

 Norris, of Birmingham, as the invisible, pale, or third 

 corpuscle, are red blood corpuscles that have be- 

 come discoloured by the mode of preparation CAlice 

 Hart). 



12. The haemoglobin of the red blood corpuscles 

 forms crystals (Fig. 10), which differ in shape in 

 various mammals. 



They are always 

 of microscopic size, 

 and of a bright red 

 colour. In man 

 and most mammals 

 they are of the 

 shape of prismatic 

 needles, or rhom- 

 bic plates; in the 

 squirrel they are 

 1 1 exagonal plates, 

 and in the guinea- 

 pig they are tetrahedral or octahedral. 



The blood pigment itself is an amorphous dark- 

 brown or black powder the hcematin ; but it 

 can be obtained in a crystalline form as hydro- 

 chlorate of h8ematin(Fig. 11). These crystals 

 also are of microscopic size, of a nut-brown 

 colour, of the shape of narrow rhombic 

 plates, and are called hcemin crystals, or 

 Teichmanris crystals. In extra vasated 

 human blood crystals of a bright yellow 

 or orange colour are occasionally met with ; they are 

 called by Virchow, their discoverer, hcematoidin. 

 They are supposed to be identical with bilirubin, 

 obtainable from human bile. 



13. The white or colourless blood cor- 

 puscles are in human blood of about ^oVo- to -5-^-5 

 of an inch in diameter, and are spherical in the 



Fig. 10. Haemoglobin crystals. 

 A, Of guinea-pig ; B, of squirrel ; c, D, human. 



Fig. 11. Hae- 

 rain crystals. 



