CHAPTER X 



DISTRIBUTION, PROPERTIES, AND 

 CHEMISTRY OF THE VITAMIN K GROUP 



1. Introduction 



The newest recognized member of the fat-sokible vitamin group is vi- 

 tamin K. The pioneer work leading to the discovery of this vitamin was not 

 begun imtil as recentlj^ as 1929. Dam^ was the first to report the develop- 

 ment of certain symptoms, such as subcutaneous and intramuscular hemor- 

 rhages, which appear in chicks on an artificial diet low in lipids. The de- 

 ficiency failed to respond to treatment with any of the vitamins known at 

 that time. Dam stated shortly thereafter^ that the disease was associated 

 with a reduction in the clotting capacity of the blood. Hemorrhages oc- 

 curred chiefly in areas exposed to injury. 



Several years later, Dam and Sch0nheyder^ came to the conclusion that 

 the hemorrhagic s\Tnptoms produced in chicks are the result of an avita- 

 minosis. The vitamin which was able to prevent these pathological symp- 

 toms was found to be present in green leaves and in certain vegetables.^ 

 It was named vitamin K,^'" inasmuch as Dam and others had most fre- 

 quently referred to it in the German and Danish literature as koagulations- 

 intamin, because it was ob\nously concerned primarily with the blood- 

 clotting mechanism. Dam, Sch0nheyder, and Tage-Hansen^-'^ demonstrated 

 that vitamin K is of importance in regulating and maintaining the normal 

 level of prothrombin in the blood. In vitamin K avitaminosis, subnormal 

 levels of prothrombin occur which can obviously account for the retarda- 

 tion or complete absence of blood clotting. In 1938, the importance of 

 vitamin K therapy in certain types of hemorrhagic conditions in man was 



1 H. Dam, Biochem. Z., 215, 475-^92 (1929). 



* H. Dam, Biochem. Z., 220, 158-163 (1930). 



3 H. Dam and F. Sch0nheyder, Biochem. J., 28, 1355-1359 (1935). 



* H. Dam, Biochem. J., 29, 1273-1285 (1935). 

 5 H. Dam, Nature, 135, 652-653 (1935). 



* H. Dam, F. Sch0nheyder, and E. Tage-Hansen, Biochem. J., 30 1075-1079 (1936). 

 ' F. Soh0nheyder, Xature, 135, 653 (1935). 



829 



