It is well known that in certain of the domestic animals, notably dogs, sheep, cats and rabbits, gallstones rarely form spontaneously and cannot be produced experimentally. Schlotthauer and Stalker1 reported the occurrence of bilirubin stones in 2 of 155 dogs studied at autopsy. Ivy2 has observed bilirubin stones in only 1 of 500 dogs whose gallbladders were opened routinely. Approximately 150 dogs were used during the course of our experiments, and calculi were never observed. The spontaneous occurrence of true cholesterol stones in dogs, sheep, cats and rabbits has not been reported. In contradistinction to these animals are certain others—chiefly human beings, oxen and hogs—in which biliary calculi occur frequently. A satisfactory explanation of the differences in the bile of these two groups of animals would do much toward accounting for some of the factors concerned in the production of gallstones.
In 1903 Harley and Barratt3 reported