HEMOGLOBIN CRYSTALS OF RODENTS' BLOOD. 199 



haemoglobin; in other words, the temperature necessary to 

 drive off the water of crystallisation is also sufficient to cause 

 certain decomposition changes in the pigment. 



My experiments have shown that squirrel's hsemoglobin will 

 under certain circumstances crystallise in forms other than the 

 usual hexagonal form. A crucial experiment in order to see 

 whether this is due to union with different amounts of water of 

 crystallisation would have been first to ascertain the amount 

 of this water in the hexagonal crystals, and then in the 

 rhombic crystals obtained by recrystallisation. I have per- 

 formed three such experiments, but the results obtained are so 

 conflicting, and exhibit variations as great as in Bohr's experi- 

 ments, that it is impossible to draw any conclusions from 

 them, except the negative one that we cannot by our present 

 methods of research make any definite statement with regard 

 to the water of crystallisation of haemoglobin. 



Even if it be found ultimately that the difference in crystal- 

 line form is dependent on varying amounts of water of crystal- 

 lisation, the difficulty is only explained up to a certain point. 

 What is left unexplained is the nature of the agency that 

 causes the haemoglobin of some animals to unite with a certain 

 amount of water of crystallisation, and that of other animals 

 with a different amount. That some such substance or agency 

 does exist would seem to be the inevitable result of the recrys- 

 tallisation experiments which have been related. 



