CRYSTALLIZATION 



315 



being rhombic, those obtained from guinea-pigs being normally 

 tetragonal and those from squirrel's blood hexagonal. 



Blood of 



Rat 

 Rat 



Squirrel 



Dog 

 Dog 



Mixed with that of 



Squirrel 

 Guinea-pig 



Guinea-pig 



Squirrel 

 Guinea-pig 



Form of hsemoglobin crystals deposited from the mixture 



Both rhombic prisms and hexagons present. 



No rhombic prisms of the shape usually seen 

 in rat's blood present. No tetrahedra. 

 Crystals are all rhombic prisms with hexa- 

 gonal habit. 



Hexagonal plates and tetrahedra both pres- 

 ent. Many tetrahedra imperfect. The 

 tetrahedra all reduced to about half the 

 size of those prepared from the unmixed 

 blood of the same guinea-pigs. 



Fine rhombic needles and hexagonal plates 

 both present in abundance. 



The greater number of the crystals formed 

 are very small tetrahedra about a quarter 

 the size of those prepared from the blood of 

 the same guinea-pigs. The optical prop- 

 erties are, however, the same. Rhombic 

 prisms, very slender, like those of dog's 

 blood, are also seen. 



According to Reichert the degree of modification of crystal 

 form induced by admixture of two bloods depends very greatly 

 upon the proportion in which they are mixed. 



In view of these facts there can be little doubt that the nature 

 of the milieu in which crystallization occurs does play an im- 

 portant part in determining the form of the crystals which are 

 deposited, and having regard to the known individuality of the 

 plasma from different biological species it would appear unneces- 

 sary to seek further for the origin of the differences in crystal 

 form of the oxyhaemoglobins derived from blood of different 

 species of animals. 



We are now in a position, also, to interpret the changes in 

 crystal-form which result from repeated re-crystallization of 

 haemoglobin (Halliburton (30) (31)), for as Wichmann (106) and, 

 more recently, Katz (45) have shown, the crystalline proteins 

 swell in or absorb the surrounding fluid menstruum in a manner 

 analogous to the swelling of jellies. A number of re-crystal- 

 lizations are therefore required to remove completely traces of 

 the original menstruum in which crystallization occurred. 



