928 PHYSIOLOGY 



35 C., cooling the solution to C., and then adding cold alcohol 

 to 25 per cent, and allowing the mixture to stand for some days at a 

 temperature of 5 to 10 C. In the case of those bloods which 

 yield oxyhaemoglobin crystals with greater difficulty, it is better to 

 add to the laked blood an equal volume of a saturated solution of 

 ammonium sulphate. The precipitate of globulins is filtered off and 

 the filtrate allowed to stand in a cool place. Crystals of hemoglobin 

 then come down in quantity. 



The crystals thus obtained are as a rule microscopic in size. Most 



FIG. 356. Crystals of oxyhaemoglobin. 

 1. From rat. 2. From guinea-pig. 3. From squirrel. 



animals yield an oxyhaemoglobin which crystallises in rhombic 

 prisms or needles belonging to the rhombic system. In the 

 guinea-pig the crystals are tetrahedral in form, while the oxyhaemo- 

 globin of the squirrel crystallises normally in the form of six-sided 

 plates. On recrystallisation, however, a squirrel's haemoglobin can 

 be obtained as a mixture of rhombic prisms with rhombic tetrahedra. 

 The water of crystallisation of oxyhaemoglobin varies in different 

 animals between 3 and 9 per cent. The solubility of the crystals 

 differs according to the animal from which they have been derived, 

 and is in direct proportion to the difficulty with which the crystals 

 are obtained. They are more soluble in highly diluted solutions of 

 ammonia and the caustic alkalies and their carbonates than in water. 

 A solution of haemoglobin will not diffuse through parchment paper ; 

 the elementary analysis of oxyhaemoglobin crystals gives somewhat 

 varying results according to the animal employed. In the case of the 

 oxyhaemoglobin of the dog Jaquet obtained the following figures : 



In 100 parts 

 C . . 53-91 54-97 



H 



N 

 Fe 



S. 



o 



6-62 . . 7-22 



15-98 . . 16-38 



0-333 . . 0-336 



0-54 0-568 



22-62 .. 20-93 



The chief differences between different animals appear to have 

 relation to the sulphur. Haemoglobin from the hen contains 0-857 per 



