THE SPECIFICITY OF HEMOGLOBIN ^.- 39 



with later in this chapter when the work of Landsteiner and Heidel- 

 berger(2) is discussed. With regard to ease of crystallisation we 

 may say at once that the haemoglobin of different animals differs 

 greatly in this respect. Ordinary laboratory practice makes one 

 familiar with the difference between, say, the blood of the horse and 

 that of the ox. Haemoglobin crystals can be obtained from the former 

 with ease, in fact it is only necessary to centrifuge horse blood in 

 a Sharpless separator, as used in Prof. L. J. Henderson's laboratory by 

 Ferry (3), to obtain them in profusion. On the other hand, quite 

 special methods are required to obtain crystals of ox haemoglobin. 

 Or again, among the rodents, rabbit's blood crystallises with difficulty, 

 that of the guinea-pig with ease. And even among the rats, according 

 to Reichert and Brown, the oxyhaemoglobins of the Norway rat and 

 of the white rat are relatively insoluble, while those of the black and 

 Alexandrine rats are much more soluble. 



The impression which one gets from this mass of information is : 



(1) That no two haemoglobins are quite the same. 



(2) That even in the same animal there is more than one form of 

 haemoglobin. Of these different haemoglobins in one animal one type 

 is more easily crystallised than another; therefore, as crystallisation 

 progresses, two or three crops of crystals may appear. These are called 

 the a-, jS- and y-haemoglobins. To quote Reichert and Brown: 



For instance, in the baboons three distinct crops of crystal oxyhsemoglobin de- 

 veloped: (1) tabular and lath-shaped orthorhombic crystals, (2) short prismatic or 

 tabular monoclinic crystals, and (3) tabular orthorhombic crystals. It is possible 

 that (1) and (3) may be the same substance, but very unlikely; (2) is evidently a 

 different substance. In the same genus two forms of methsemoglobin were observed, 

 one orthorhombic and one monoclinic, corresponding to the a- and ^-haemoglobins. . . . 

 Among the rodents two forms of haemoglobin were observed in a number of species. . . . 

 Thus, in the blood of the domestic rabbit an orthorhombic and a monoclinic form of 

 oxyhaemoglobin are found that are evidently different. 



The crystals of -haemoglobin are also dimorphous in the horse, the 

 marmot and many other animals. 



Crystals pi the species of any genus belong to the same crystallographic system 

 and generally to the same crystallographic group; and they have approximately the 

 same axial ratios, or their ratios are in simple relation to each other. In other words, 

 the hcemoglohin crystals of any genus are isomorphous. In some cases the isomorphism 

 may be extended to include several genera, but this is not usually the case, unless, 

 as in the case of the dogs and foxes for example, the genera ^re very closely related. . . . 



Where several kinds of haemoglobin are to be looked for in one 

 species of a genus, they are to be looked for in other species of the 



