188 W. D. HALLIBURTON. 



The matter must therefore be left incomplete up to this 

 point for the present. The probability, however, is greatly in 

 favour of the crystals being true hexagons. 



We have seen that in order to have a rhombic plate with 

 hexagonal habit, it is necessary that one of its angles be 

 approximately 120°. I measured the angles in the rhombic 

 plates found in the rat, and found that they averaged 129°. 



I shall also presently show that it is possible by the inter- 

 mixture of the blood of different animals to obtain crystals 

 closely resembling hexagons, but which are not so, as is shown 

 by their optical properties. 



b. Mouse. — Kunde was the first to describe the haemoglobin 

 crystals of this animal. He made eighteen observations, and 

 the crystals he found were fine needles and prisms. 



Bojanowski 1 was the next to make observations on these 

 crystals. He describes and figures them as six-sided plates 

 resembling in form those from squirrel's blood, of a flesh 

 colour, and very soluble in water. He prepared them by the 

 addition of a mixture of equal parts of alcohol and ether to 

 the blood. No description of their optical properties is given. 

 He remarks, " I have not been able to observe the fine needles 

 described by Kunde." 



Preyer repeated these experiments, and confirmed the obser- 

 vations of Kunde, not those of Bojanowski. He obtained 

 small prismatic crystals. 



I have myself experimented with the blood of eighteen 

 mice, and the result has been again to confirm Kunde's obser- 

 vations. The crystals are exceedingly difficult to obtain, and 

 in some cases I have had to repeat the process of freezing and 

 thawing many times after the addition of alcohol, before suc- 

 ceeding in obtaining them. They are very soluble in water. 

 The crystals are exceedingly small rhombic prisms. They are 

 nearly colourless, and it is only when they are heaped together 

 that any red tinge at all can be perceived in them. In one 

 case in which by the addition of ether to the blood I obtained 

 crystals of fair size after allowing the mixture to stand for five 

 1 Bojanowski, ' Zeitscli. f. wiss. Zool.,' Bd. xii, 1863, p. 333. 



