9D 



A TEXTBOOK OF PHYSIOLOGY 



are immediately dissolved. On the other hand, blood kept at for 

 several days (three to four) can be reinjected into an animal and still 

 functionate. Haemoglobin plays a considerable part in the transport 

 of carbon dioxide from the tissues to the lungs. It has a specific 

 capacity for absorbing carbon dioxide.- 



The Fate of the Red Blood-Corpuscles. It is not possible to say 

 how long the red corpuscle circulates before it is destroyed, possibly 

 three to four weeks. After some such time the corpuscle is probably 

 destroyed in the spleen, the liberated haemoglobin passing to the liver 

 to be disintegrated there. From it the iron-free bile-pigments bilirubin 

 and biliverdin are formed, the iron being stored in the liver. 



This iron can be stained blue by treating sections of the liver 

 with potassium ferrocyanide and hydrochloric acid, or black by a 

 pure solution of haematoxylin. 



The iron in the liver is greatly increased in conditions in which a 

 large destruction of red corpuscles takes place. It has been suggested 

 that the spleen regulates the iron metabolism of the body; and it is 

 possible that some of the destruction of red corpuscles takes place 

 there, accompanied by the formation of pigment and the storage of 

 iron in the splenic cells. It is supposed that the stored iron is again 

 used to form haemoglobin. 



Chemistry of the Red Corpuscle. The framework, or stroma, 

 consists of protein and lipoids, within which are the salts, notably 

 salts of potassium, and the haemoglobin (see table, p. 81). 



The pigment haemoglobin forms 90 per cent, of the corpuscle. It 

 is one of the compound proteins, a chromoprotein consisting of an 

 iron-containing portion (haematin) and a protein portion (globin); 

 the latter is a histone. 



Haemoglobin, as other proteins, varies in composition in different 

 animals. 



Its percentage composition is approximately 



C 54-71; H 7-38; N 17-43; S 0-79; Fe 0-399; 19-602. 



Haemoglobin is readily soluble in water; coagulated by heat to 

 a brown coagulum; dextrorotatory to polarized light. It can be 

 obtained in crystalline form, but more readily from some bloods 

 than others. It is easily obtained from the blood of the rat after 

 the addition of distilled water. In the guinea-pig's blood haemolysis 

 is first produced by the addition of chloroform or ether. Upon 



