In a preliminary report1 the reason for this study was pointed out to be an injury of the hepatic artery sustained by a boy, aged 12 years, who was run over by a wagon, the wheels passing over the epigastric region. He had all the symptoms of an internal hemorrhage. At operation, the hepatic artery was found to be severed. Both ends of the artery were tied. The boy did well until the tenth day, when he developed a slight jaundice, accompanied by vomiting. He died on the fourteenth day, of symptoms resembling acute yellow atrophy of the liver. A postmortem examination was refused. Our desire to duplicate this injury in animals has developed these experiments.In our preliminary studies, rabbits were used exclusively; but in our later experiments, dogs, cats, guinea-pigs and rabbits were employed.These animals may be divided into the carnivorous and herbivorous types. We found the former particularly resistant to the effects of the ligation of the hepatic artery, while the latter succumbed in every instance. This difference in their susceptibility to the ligation may be due to changes in the metabolism in these two types of animals. This problem is occupying our attention at the present time and the results will be reported in the near future.However, the anatomic variations may be a sufficient reason alone to cause such a tremendous difference in the mortality rate of the different animals. To arrive at a definite conclusion concerning the difference in the ability of these animals to resist the ligation performed in a similar manner, a study of the comparative anatomy of the four animals used was deemed essential (Figs. 1, 2, 3 and 4).