20 HEMOGLOBIN. 



contain inorganic salts, which differ from those of the 

 plasma, in the replacement of sodium by potassium. 



The body of the corpuscles consists chiefly of globulins 

 associated with lecithin and cholesterin. The globulin is of 

 two kinds, the greater part resembling paraglobulin, the 

 remainder having the characters of myosin. The colour- 

 less corpuscles also contain glycogen, and are, like the 

 coloured corpuscles, relatively rich in potassic salts. The 

 nuclei contain a non-crystallizable nitrogenous body 

 (nuclein not a proteid) which is insoluble in weak acids, 

 and hence in gastric juice, but dissolves very readily in 

 weak alkalies. The chemical relations of this substance 

 are as yet unknown. It is found in all nuclear structures, 

 e.g., in spermatozoids. The " protoplasm " of the colour- 

 less corpuscles consists chiefly of globulin associated with 

 lecithin and cholesterin. It contains glycogen. 



In normal blood, haemoglobin exists only in the cor- 

 puscles, but in certain diseased states it is dissolved in the 

 plasma and is then crystallizable : the nature of the 

 change it undergoes is not known. A similar change is 

 produced artificially by repeated freezing and thawing, by 

 subjecting blood to a temperature of 60 C, or by the 

 action of ether or chloroform. The property which the 

 blood possesses of absorbing oxygen from the inspired air, 

 and of giving it up to the living tissues with which it is 

 brought into contact in the circulation, is due to its 

 haemoglobin. 



Hamoglobin crystallizes from its solution, in forms which vary according to 

 the animal from which it is derived. The crystals are of the colour of 

 arterial blood, but become dark, without changing their form, when placed 

 in vacua at a low temperature. They then exhibit two colours, looking green 

 along the edges, purplish-red elsewhere : on the admission of air or oxygen, 

 the colour is restored. 



Haemoglobin is very soluble in warm water, much less so in cold, but, in 

 this respect, crystals obtained from different animals differ : thus, the hgemo- 

 globin of the rat or guinea-pig is less soluble than that of man, and is much 

 more prone to crystallize. 



