HEMOGLOBIN CRYSTALS OF RODENTS' BLOOD. 195 



by mixing that from two animals in which the crystalline form 

 is different. It also shows that rhombic haemoglobin crystals 

 may assume a hexagonal type (fig. 4). These crystals are not, 

 however, perfect or equilateral hexagons, two of the sides 

 being longer than the other four. 



Fig. 4. 

 A H 



The side a. B = E D = - 0019 m. (average). 



The sides bc = CD = e? = ja= '00125 m. (average). 



This irregularity is possibly to be accounted for by the fact 

 that, in rats' haemoglobin crystals, the angles corresponding to 

 bcd, a f e, are 51°. In order to obtain perfect hexagons 

 of a rhombic type it is necessary, as before stated, that this 

 angle be 60°. 



Under crossed nicols these crystals appear perfectly bright, 

 so contrasting with the true hexagons obtained from the blood 

 of the squirrel and hamster. 



This result was not, however, always obtained ; in one or two 

 cases I obtained as a result of mixing the blood of these two 

 animals a mixture of crystals; that is prisms and tetrahedra. 



5. Can Squirrel's Haemoglobin be obtained in any form other 

 than Hexagonal Crystals ? 



Another set of experiments was performed with the object 

 of breaking down the hexagonal constitution of the haemo- 

 globin of squirrels' blood. The first method tried was that of 

 driving off the water of crystallisation, and of then adding 

 water to the dehydrated hasmaglobin. 



The haemaglobin was obtained in a state of purity and dried 

 over sulphuric acid until it lost no more weight. Then it was 

 examined, and found to have its normal spectroscopic proper- 



