The relative frequency of stones composed chiefly of calcium and phosphorus in the urinary tract as compared with their occurrence in other excretory systems such as the lower intestine, biliary and pancreatic systems and the salivary glands has made a study of the local metabolism of these elements by the urinary tract of some importance. I1 have indicated elsewhere in a preliminary report the rather unexpected action of the urinary tract on certain connective tissues in the production of bone. These observations will be discussed in detail in this article, and further observations relative to osteogenesis will be presented.
The presence of bone elsewhere than in the skeleton has been of considerable interest to the students of osteogenesis. An extensive literature dealing with this subject exists, of which a few striking examples may be cited. Apparently the most frequent site of heteroplastic bone is the sclerotic artery;2 next