204 HAEMOGLOBIN. 



able aggregations of the smaller crystals, exhibit, like aggregations of 

 Mood corpuscles, the red colour characteristic of the blood. 



We shall now examine successively the most important facts con- 

 nected with the (1) form, (2) quantity of water of crystallisation, 

 (3) solubility, presented by crystallised oxyhsemoglobin, (4) diffusibility. 



1. Form. (a) The blood of man and of the immense majority of 

 animals yields oxyheemoglobin which crystallises in rhombic prisms or 

 needles belonging to the rhombic system. 



(&) The oxyhtemoglobin of the guinea-pig presents crystals which 

 were described by Lehinann as regular octohedra. They were, however, 

 shown by the eminent crystallographer v. Lang 1 to be tetrahedra 

 belonging to the rhombic system. 



The blood of certain birds, 2 and occasionally apparently of the 

 rat 3 , 4 , 5 , yields crystals of the same form. 



(c) The oxyhremoglobin of the squirrel crystallises normally in the 

 form of six-sided plates belonging, as proved by v. Lang, to the hexagonal 

 system. These crystals had been first described by Lehmann and Kunde. 

 The blood of the hamster (Cricetus vulgaris) contains oxyhaemoglobin 

 which crystallises, as Lehmann showed, in rhombohedra and six-sided 

 plates belonging to the hexagonal system. Halliburton, 6 who has studied 

 the crystallography of oxyhaemoglobin with great care, has made the 

 interesting observation that " after recrystallising squirrel's hc^moglobin 

 several times the hexagonal constitution of the crystals is broken down, 

 and the crystals obtained are either rhombic prisms or a mixture of 

 these with rhombic tetrahedra." 



Rollett, 7 taking for granted that oxyhsemoglobin, from whatever source 

 obtained, possessed the same chemical composition, argued, from the fact of 

 its crystallising generally in the rhombic, but in the case of the squirrel in the 

 hexagonal system, that oxyhaemoglobin should be looked upon as dimorphous. 



Halliburton, however, with perfect correctness, hesitates to admit this 

 view, which could only be held if we were certain that the haemoglobins whose 

 crystals belong to different systems possess identical composition, and suggests 

 that perhaps the difference in the crystalline form, as well as the difference in 

 solubility of the haemoglobins which crystallise differently, depends upon 

 varying quantities of water of crystallisation that, in fact, the haemoglobins 

 which crystallise in different systems represent "different hydrates of oxy- 

 haemoglobin." 8 This may be the case, though it appears to me that the cause 

 of the difference lies deeper. 



It has been previously stated and the grounds for the statement will be 

 given in a subsequent section that, notwithstanding the perplexingly dis- 

 cordant results of the analyses of oxyhaemoglobin, there is, in the haemoglobin 

 of all animals, absolute identity of the essential iron-containing nucleus, i.e. 



1 In a paper by A. Rollett, entitled "Versuche u. Beobachtungen am Blut, nebst 

 krystallographisch. u. optisch. Mittheilmigen ueber die Blutkrystalle von v. Lang," 

 Sitzungsb. d. k. Akad. d. Wissenseh., Wien, 1862, Bd. xlvi. S. 66-98. 



" Halliburton, "Text Book of Chemical Physiology," London, 1891, S. 270. 



3 , 4 Kunde, Lehmann, see Preyer, "Die Blutkrystalle, " S. 38. 



5 Hoppe-Seyler, "Ueber die Krystallformen der Blutkrystalle," Med. Ohem. Untersuch. , 

 Berlin, 1868, S. 195. 



6 "Preliminary Communication on the Haemoglobin Crystals of Rodents," Journ. 

 PhysioL, Cambridge and London, 1886, vol. vii. p. 2 ; Quart. Journ. Micr. Sc., London, 

 vol. xxviii. p. 181. 



7 LOG tit. 



8 Halliburton, "Text Book of Chemical Physiology," section on the "Crystallography of 

 Oxyhfiemoglobin," pp. 270-274. The student is recommended to read this interesting and 

 suggestive section. 



