A day-to-day study has been made of the sediment in the sterile liver bile of intubated dogs. There exists a marked tendency for calcium carbonate to be deposited therefrom. After hepatic or duct injury a great deal of organic débris of various sorts may be present in the bile, but it never causes deposition out of the fluid save when it accumulates in quantity on the tube wall. Particles of the material of which "bile thrombi" are composed may be found in the bile when the liver has been appropriately damaged, but these fail to act as centers of stone formation. On the other hand, there are to be found in the secretion after many sorts of hepatic injury little nuclei which undoubtedly serve in this way. These nuclei consist of a mixture of calcium bilirubinate and carbonate with an organic shadow or scaffolding. They do not occur in normal bile, but, coming down on special occasions, prove favorable to deposition out of the secretion elaborated at later periods. We have found nuclei strikingly similar in their relationship to stone formation, but consisting almost wholly of carbonate, in the sterile bile from human gall bladders which contained large calculi. Many of them were encountered in a free state, and others with layers of cholesterol and organic matter upon their surface, while others yet were recognizable deep within matured stones.

The factors concerned in the genesis of gall stones consisting of calcium carbonate have been reviewed at some length in this paper and the preceding one. The evidence we have collected supports the view that the development of carbonate stones in human beings as well as in the dog may be a consequence, not of changes in the bile brought about by microorganisms, nor of the elaboration of an inflammatory exduate rich in calcium salts, but merely of inflammation such as leads to lessened motility of the duct system with the accumulation of organic débris. The fact that infection is almost the sole agent whereby such inflammation is set up and maintained in clinical instances had led too often to the conclusion that it serves as the essential agent in the process of calcification.

The present findings taken with those described in a preceding paper suffice for an understanding of the immediate history of the gall stones which develop in intubated dogs. But the factor of individual differences, as yet undefined in nature, bulks large in the problem of the lithiasis, as does that of the local physiological safeguards against it.

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