Evidence is presented that the proliferating gall bladder epithelium in the dog and guinea pig is capable of stimulating bone formation in certain connective tissues such as the abdominal wall. Other connective tissue areas such as the subepithelial connective tissue of the gall bladder and urinary bladder do not share in this tissue reaction and resist the bone stimulus of the epithelium. The formation of bone in these circumstances is thus biphasic.

A difference between connective tissues morphologically identical can be proven physiologically, by their response to the osteogenic stimulus of appropriate epithelia.

Calcium carbonate microliths occurred in the mucus of the occluded gall bladder in which there was transplanted connective tissue forming part of the wall.

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