CRYSTALLIZATION 



315 



being rhombic, those obtained from guinea-pigs being normally 

 tetragonal and those from squirrel's blood hexagonal. 



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. 



