252 VITAMIN D GROUP 



restores the normal phosphorus absorption which was secondarily impaired 

 by defective calcium al)S()rption and the formation of slightly soluble phos- 

 phates of calcium. (3) It increases urinary phosphorus excretion, although 

 phosphorus clearance actually is decreased because of increased tubular 

 resorption of phosphorus. This is accomplished presumably by the inhibi- 

 tory effect of increased plasma calcium upon parathyroid hormone secre- 

 tion. In the absence of the parathyroids phosphorus clearance is actually 

 increased by vitamin D intake. 



Thus with more calcium and inorganic phosphorus a^'ailable from exog- 

 enous sources and improved phosphorus resorption by the kidney, normal 

 levels of both elements are m.aintained, and normal minerplization of bone 

 is restored. Whether parath^a'oid hormone acts not only through the kidneys 

 but also directly on the bone itself is not known. 



In the serum of normal children the concentration of calcium is rem.ark- 

 ably constant, at about 10 ± 1.5 mg. %. The inorganic phosphorus content 

 of the serum is also fairly constant and in normal children is usually about 

 6 ± 1 mg. %. In the newborn infant the calcium content of the blood serum 

 may vary between 7.0 mg. and 11.0 mg. per 100 ml. The inorganic phos- 

 phorus content of the blood in premature and newborn full-term infants is 

 5.0 to 6.0 mg. %; it is slightly loAver after 3 years of age, and still lower in 

 adults. It has been dem.onstrated that, whereas in tetany there is regularly 

 a marked reduction in the calcium of the serum, the drop in rickets is in- 

 frequent and may be caused l)y other factors than the vitamin D deficiency. 

 There is, however, a constant and sometimes marked decrease in the con- 

 centration of inorganic phfjsphorus with patients suffering from, rickets. 

 Rowland and Kramer'^ and h-erson and Lenstrup^ independently made 

 observations with respect to inorganic and pcicl-soluhle phosphorus in 

 patients with rickets and found that it varied from 0.6 to 3.2 m^. per 

 100 ml., the average being 2.0 mg., or less than 50% of the normol eerum 

 content. Rowland and Kramer showed that the administration of cod liver 

 oil in therapeutic doses had no efect on the calcium concentration but did 

 result in a marked increase of the phosphorus level. 



We may say, therefore, that there is a fairly constant and a clinically 

 significant deficiency of the inorganic phosphorus of the plasma in rickets. 

 Rowland and Kramer de\'eloped a mathematical formula which deter- 

 mines the chemical reciuirements for normal bone deposition.'* They found 

 that in most cases of uncomplicated rickets if the product of calcium con- 

 centration in milligrams per cent and the inorganic phosphorus concentra- 



^J. Howland and B. Kramer, ,1///. ./. Diseases Chihiren 22, 105 (1!)21). 

 ' P. Iverson and K. Lenstruj), Forhandlinf/erne Ved. Forste Nonliske Kongres for 

 Pediatri. 1920. 

 . Howland and B. Kramer, Trans. Am. Pediat. Sac. 34, 204 (1922). 



