Vitamin K
In 1929 Dam reported that chicks developed a hemorrhagic condition and prolonged blood otting time when raised on specific synthetic rations. In 1935 he proposed the term vitamin K oagulations-vitainin) for a factor in certain foods which protected chicks against this emorrhagic syndrome. Primarily the affected chicks exhibited internal hemorrhage and ?I"Olonged blood-clotting time (up to several hours in some cases). Many foods were tested for :itamill K activity by Dam, and he reported that hog liver was very high, cod liver oil practically evoid of activity, and egg yolks low in activity. Among the vegetable material tested, hemp seed as found to be an excellent source.
The factor was found to be fat soluble; even large amounts of the other fat-soluble vitamins nad no beneficial effect on the course of the syndrome. Thus vitamin K was differentiated from the other fat-soluble vitamins A, D, and E. Another group of investigators had been working along similar lines and reported similar findings. In 1935 Almquist and Stakstad reviewed the earlier
ork done in their laboratory and showed that fish meal was an excellent source of the antihcmorrhagic factor, or vitamin K.
It was especially interesting that, during slight putrefaction the fish meal improved as a source of this factor. They also showed that in alfalfa the factor was localized in the unsaponifiable fraction ofthe ether extract. It was logical that workers in this field initiated attempts at isolation of the active principle or principles in the products found to be the best sources. Dam, Karrer and their co-workers isolated the vitamin from alfalfa in 1939. In the same year Doisy and associates isolated the principle from both alfalfa and fish meal. It was evident that the vitamin from alfalfa was chemically different from the product obtained from fish meal. Vitamin K, was used to designate the former and vitamin K, the latter. Synthesis of vitamin K was accomplished by various workers in 1939.
