PREPARATION OF HAEMOGLOBIN CRYSTALS. 



in muscle, and in traces in the fluid part of blood, but in this last case 

 only as the result of the solution of some red corpuscles. Its per- 

 centage composition is : C 53'85, H 7'32, N 16-17, Fe 0'42, S 0'39, 

 O 21 '8 4 (dog). Its rational formula is unknown, but Preyer gives 

 the empirical formula C 600 , H 960 , N 164 , Fe, S 3 , 179 . Although it is a 

 colloid substance it crystallises (Hiinefeld 1840, Reichert) in all classes 

 of vertebrates, according to the rhombic system, and chiefly in rhombic 

 plates or prisms ; in the guinea-pig in rhombic tetrahedra (v. Lang); 

 in the squirrel, however, it yields hexagonal plates. The varying 

 forms, perhaps, correspond to slight differences in the chemical com- 

 position in different cases. 



Crystals separate from the blood of all classes of vertebrata during 

 the slow evaporation of lake-coloured blood, but with varying facility. 



The colouring-matter crystallises very readily from the blood of man, dog, 

 mouse, guinea-pig, rat, cat, hedgehog, horse, rabbit, birds, fishes ; with difficulty 

 from that of the sheep, ox, and pig. Coloured crystals are not obtained from the 

 blood of the frog. More rarely a crystal is formed from a single corpuscle 

 enclosing the stroma. Crystals have been found near the nucleus of the large 

 corpuscles of fishes, and in this class of vertebrates colourless crystals have been 

 observed. 



Haemoglobin crystals are doubly 

 refractive and. pleo-cliromatic ; they 

 are bluish-red with transmitted light, 

 scarlet-red by reflected light. They 

 contain from 3 to 9 per cent, water 

 of crystallisation, and are soluble in 

 water, but more so in dilute alkalies. 

 They are insoluble in alcohol, ether, 

 chloroform, and fats. The solutions 

 are dichroic; red in reflected light, 

 and green in transmitted light. 



In the act of crystallisation the haemoglobin 

 seems to undergo some internal change. 

 Before it crystallises it does not diffuse like 

 a true colloid, and it also rapidly decomposes 

 Fig. 8. hydric peroxide. If it be redissolved after 



, ,. . , , - crystallisation it diffuses, although only to 



Haemoglobin crystals a, b, from ' , 



, , j f a small extent, but it no longer decomposes 



human blood ; c, from the cat ; , . , ' , . , . -, , ... 



, ,. . hvdric peroxide, and is decolourised by it. 



d, from the guinea-pig; e, / bod / like an acid is deposited from 

 hamster ; f, squirrel. . Qf & 



12, Preparation of Haemoglobin Crystals. 



Method Of Rollett. Place defibrinated blood in a platinum capsule, allow 

 the capsule and the blood to freeze by setting them in a freezing-mixture, and 



