Chapter I X 



VITAMIN Bi2 (ERYTHROTIN) 



I. INTRODUCTION 



In 1926, G. R. Minot and W. P. Murphy^ demonstrated that 

 patients with pernicious anaemia could be maintained in normal 

 health by ingestion of liver. Subsequently it was discovered that the 

 injection of liver extracts gave more reliable results with less incon- 

 venience to the patients. Since that time, the use of liver extracts 

 has become routine practice in the treatment not only of Addisonian 

 pernicious anaemia, but also of pernicious anaemia due to tapeworm, 

 pernicious anaemia of pregnancy, nutritional megaloblastic anaemia, 

 megaloblastic anaemia of infancy and childhood and megaloblastic 

 anaemia accompanying steatorrhoea. Three types of liver extracts 

 are in use — " refined " extracts with a relatively low concentration of 

 total solids derived from a large amount of liver, " crude " extracts 

 with a much higher total solids content and " proteolysed " extracts 

 in which the liver tissue is partially broken down before extraction in 

 order to liberate more of the active principle. Some anaemias respond 

 more readily to proteolysed and crude liver extracts than to refined 

 extracts and there are many clinicians who maintain that refined 

 extracts fail to keep the blood picture normal for more than a limited 

 period. 



Folic acid, as has already been pointed out (page 484), is an anti- 

 anaemic factor that is only successful in megaloblastic forms of 

 anaemia ; it has no effect in subacute combined degeneration of the 

 cord, and may actually increase the severity of the nervous symptoms 

 in pernicious anaemia. Clearly folic acid is different from the substance 

 in liver extract that cures pernicious anaemia, and potent refined liver 

 extracts do, in fact, contain negligible amounts of folic acid. 



Attempts to fractionate liver extracts with the object of isolating 

 the antipernicious anaemia factor have always been difficult because 

 no chemical test for the factor exists, and no animal or micro-organism 

 was known that would respond specifically to the factor. The isolation 

 of more or less pure preparations of the anti-pernicious anaemia factor 

 was announced in the same week by E. L. Smith ^ and Rickes et al} 

 The former obtained by chromatography two red pigments from an 



530 



