Karl Link and Warfarin

Karl Paul Gerhard Link (31 January 1901 - 21 November 1978) was an American biochemist best known for his discovery of the anticoagulant warfarin.



In the subsequent years, most of his research focused on plant carbohydrates. However, the most fruitful period began when Ed Carson, a Wisconsin farmer, attracted Link's attention to sweet clover disease, described in 1924 by veterinarian Frank Schofield. In this condition, cows bled to death after consuming hay made from spoilt sweet clover. Carson's stock had been affected, and he brought a dead cow, blood that would not clot, and 100 pounds of sweet clover hay. Under the direction of Link, PhD students Harold Campbell, Ralph Overman, Charles Huebner, and Mark Stahmann crystallised the putative poison - a coumarin - and synthetised and tested it; it turned out to be dicumarol (3,3'-methylenebis-(4 hydroxycoumarin)).



Dicumarol was subjected to clinical trials in Wisconsin General Hospital and the Mayo Clinic. It was for several years the most popular oral anticoagulant.


Warfarin, one of the several compounds synthesised as part of the coumarin research, was patented in 1945 with the Wisconsin Alumni Research Foundation, Link and researchers Stahlmann and Ikawa jointly owning the patent. Initially marketed as rat poison, warfarin would later, in the 1950s, become the second most important anticoagulant for clinical use (after heparin).

Neisser and the flow of seed

Neisseria gonorrhoeae, a gram-negative intracellular diplococci, was identified in 1879 by the German physician, Albert Neisser, and is the causative agent of gonorrhea, one of the oldest recognized sexually transmitted diseases.

The term "gonorrhea" is derived from the Greek language and literally means "flow of seed"; this term was used to describe the white milky appearance of the purulent urethral discharge, which was mistaken for semen.


Neisser was also the co-discoverer of the causative agent of leprosy. In 1879 the Norwegian physician Gerhard Armauer Hansen gave to young Neisser (who had visited him in Norway to examine some 100 leprosy patients) some tissue samples of his patients. Neisser successfully stained the bacteria and announced his findings in 1880, claiming to have discovered the pathogenesis of leprosy. There was some conflict between Neisser and Hansen, because Hansen had failed to culture the organism and demonstrate unequivocally its link to leprosy, although he had observed the bacterium since 1872.