The present work embodies studies on the problem of fibrin regeneration in rabbits deprived of the entire liver (1).In the past the formation of fibrinogen has been ascribed to various organs. Claude Bernard in 1848 (2), Lehmann (3), and Brown-S6quard (4) believed they had found the blood of the mesenteric veins rich in the substance and the content of the hepatic and renal veins relatively poor. Years later these findings seemed to be confirmed by the work of Dastre (5-8). As result the liver was credited with the function of fibrinogen destruction while certain other organs, particularly the intestine, were looked upon as its chief site of origin. By others, in the meantime, the lungs and skin (6), the bone marrow (9, 10), and leucocytes (11) have been thought to form it. The more important of these views will be considered further on in connection with our findings.In 190S Doyon (12, 13) and his associates found that extensive degenerative changes in the liver were accompanied by a fall in the blood fibrinogen content of dogs poisoned by chloroform and phosphorus. They suggested the liver as a probable source of fibrinogen. In the last quarter of a century this view has steadily gained acceptance. Nearly all workers on the question of the origin of fibrinogen are now agreed that the liver is its chief source. Whipple andHurwitz" (14) have determined a striking correspondence between the extent of fiver damage and the decrease of blood fibrinogen in dogs poisoned by chloroform and phos-/ phorus, and they have suggested an hepatic origin of this blood protein. Goodpasture (15), studying fibrinogen regeneration in dog's blood, agreed with this view in part but concluded that the intestines act as a controlling if unessential factor in fibrinogen formation. More will be said of this view further on.It remained for Meek (16) to demonstrate clearly a r61e for the liver in fibrinogen formation, This author proved that the substance is regenerated in the Eck fistula dog. But if ligation of the hepatic artery was practiced in addition and the occlusion of the portal vein made close to the liver after formation of the Eck fistula, no regeneration whatever occurred. Indeed there followed a depletion of the amount already present in the blood.In a series of studies on fibrin metabolism in the dog, under normal and pathological conditions, have recently brought further 569 on