CHAP. II.] THE BLOOD. 89 



In 100 parts. 



C 5400 



H 7-25 



N 16-25 



Fe 0-42 



S 0-63 



O 2145 



100-00 



and assuming that the molecule contains one atom of iron the follow- 

 ing would be the empirical formula : 



CH 960 N 154 FeS 3 179 . 



Crystalline 

 form. 



Oxy-haemoglobin obtained from the blood of man 

 and the majority of the lower animals, crystallizes in 

 prisms or rhombic plates of a beautiful blood-red colour, which belong 

 to the rhombic system ; the oxy-haemoglobin of the squirrel crystal- 

 lizes in six-sided plates which belong to the hexagonal system. The 



FIG. 15. CRYSTALS OF OXY-HAEMOGLOBIN. 



a, b, c and e illustrate the forms in which haemoglobin separates from the blood of 

 man and the majority of mammals, d are tetrahedral crystals from the blood of the 

 guinea-pig. / are hexagonal crystals from squirrel's blood. 



