HEMOGLOBIN CRYSTALS OF RODENTS* BLOOD. 189 



days, the crystals still showed this same peculiarity, namely, in 

 being nearly colourless. I have successfully employed Boja- 

 nowski's method for the preparation of the crystals, namely, 

 the addition of a mixture of alcohol and ether to the blood ; but 

 in no case did hexagonal crystals form. Mouse's haemoglobin 

 also differs from squirrel's in being very soluble in water ; this 

 is admitted by Bojanowski; one would therefore expect a 

 priori that its crystalline form would be different. 



c. Hamster (Cricetus vulgaris). — My remarks under 

 this heading will be only historical. I have not myself been 

 successful in obtaining one of these animals. The crystalline 

 form of the haemoglobin was first described by Lehmann, who 

 found rhombohedra and six-sided plates. His experiments 

 were repeated by Preyer,! whose observations on the subject are 

 very complete. He fornd both crystalline forms, viz. six- 

 sided plates, and rhombohedra. This is interesting since the 

 rhombohedron belongs to the hexagonal system. By examina- 

 tion between crossed nicols he found that the six-sided plates 

 had no action in " depolarising " the ray, and he therefore con- 

 cludes that they, like squirrel's haemoglobin crystals, are true 

 hexagons. 



d. Conclusions. — The presumption in favour of the 

 haemoglobin crystals of the squirrel and hamster being true 

 hexagons is exceedingly great. In the case of the mouse, it 

 seems to be almost equally certain that the crystals are not as 

 a rule hexagonal. I should not like, however, to deny that 

 haemoglobin may sometimes in the case of the mouse crystallise 

 in this way, because of some observations I have made on the 

 haemoglobin crystals of the rat. 



Crystals are obtained from the blood of this animal with 

 great ease; mere addition of water to the blood causes almost 

 immediately an abundant crop of crystals. On this account 

 the blood of this animal is used by the students in the practical 

 classes at University College for the preparation of haemoglobin 

 crystals. Professor Schafer told me that on looking over the 

 students' preparations he had occasionally seen hexagons to- 

 1 « Die Blutkrystalle,' p. 262. 



