PHYSIOLOGICAL CHEMISTEY 339 



THE HAEMOCYTES OR RED BLOOD CORPUSCLES. 



Structurally these are said to consist of a stroma containing in its 

 meshes a chromo-protein called Haemoglobin. It is, however, impossible 

 to demonstrate this stroma histologically, and some authorities believe 

 that the haemoglobin is merely contained in a colloidal state in a 

 protein envelope. 



Chemically they contain about 60 % of water and nearly 36 % of 

 haemoglobin, the remaining 4 % represented by the so-called stroma 

 consisting of lecithin, cholesterol and nucleo-protein. 



Haemoglobin. This is a compound protein containing 0'4 % of iron. 

 When decomposed by acids or alkalies it splits up into a protein of 

 the nature of a histone (see p. 305) called globin and into a pigment 

 called haematin, which contains all the iron. A pure solution of 

 haemoglobin can be obtained by centrifugalising defibrinated blood, 1 

 removing the serum with a pipette, shaking up the corpuscles with a 

 0*85 % sodium chloride solution 2 (which is nearly isotonic for the blood 

 of the ox, horse, or man), and again centrifugalising. 



By this means the corpuscles are thoroughly washed free of serum, 

 etc. They are then collected and treated with two or three times their 

 bulk of distilled water, in this the haemoglobin dissolves, a deep red 

 solution resulting. 



EXPERIMENT VIII. Heat carefully some haemoglobin solution. It 

 decomposes at about 60 C., and the protein coagulates on further 

 heating. Also test the solution for protein ; it gives several of the 

 ordinary protein reactions, but in each case a splitting into protein 

 and haematin simultaneously ensues. 



Besides being dissolved out by distilled water the haemoglobin may 

 be set free from the red corpuscles by (i) warming to 50 C.; (ii) the 

 addition of a little ether, or of dilute ammonia solution; (iii) the 

 addition of bile, saponin, or the serum of another species of animal. 

 The " laking " of blood can be recognised by the greater translucency 

 of the laked blood (see also chapter on Haemolysis). 



EXPERIMENT IX. Compare tubes of : 



(a) whipped blood diluted with distilled water ; 



(b) whipped blood diluted with physiological saline. 



1 Horses' blood should be used for this purpose as the corpuscles sink more 

 quickly than do the corpuscles of any other blood. 



2 A salt solution of this strength has the same osmotic pressure as the contents 

 of the red blood corpuscle, and consequently no swelling or crenation of the 

 corpuscle is produced. 



