266 VITAMIN D GROUP 



the vitamin is administered, the status of the endocrine system, and the 

 age of the patient. 



The story of vitamin D, its identification as a separate calcifying vitamin, 

 its isolation in pure form, and its application in eradicating what was a 

 serious and crippling disease, represents a brilliant chapter in sterol chem- 

 istry, in nutritional physiology, and in clinical medicine. However, little 

 is known as to its action. In some mysterious manner it facilitates the ab- 

 sorption of calcium from the intestinal tract and deposits it as a phosphate 

 or carbonate in osteoid and cartilage matrix. It controls in part the clear- 

 ance of inorganic phosphorus by the kidney, and still more remarkably it 

 molds the deformed tissue of the ricketic animal into a normal configura- 

 tion and pattern characteristic of the involved tissue. Little is known con- 

 cerning the mechanism of absorption of the vitamin itself, its manner of 

 transport, or its storage in the tissues. Much has been revealed, much still 

 remains to be discovered. Newer methods are needed for these studies. 



