VITAMIN D 317 



rickets-producing diets. This diet has been adopted by the Council on 

 Pharmacy and Chemistry of the American Medical Association for 

 standardizing viosterol. 



The Steenbock-Black diet and line test technique are also used in 

 the quantitative determination of vitamin D in the Pharmacological 

 Laboratory of the Pharmaceutical Society of Great Britain. Coward 

 (1928), in describing the technique followed in these laboratories, has 

 proposed to overcome the difficulties involved in expressing results 

 obtained in different laboratories by the adoption of a standard prepara- 

 tion of the vitamin in question. The standard recommended is a prepara- 

 tion of irradiated ergosterol of such potency that a daily dose of not 

 more than 0.0001 milligram will under the conditions of the experiment 

 cause complete healing of the induced rickets. By equating by means of 

 the line test, the dosage of the material being tested with the dosage of 

 the standard irradiated ergosterol required for complete heaUng, it is 

 possible to calculate the amount equivalent to the standard dose of 

 0.0001 milligram. The amount may then be expressed as the number of 

 units of antirachitic potency contained in any convenient measure of the 

 material being tested. 



Using a solution of irradiated ergosterol prepared under conditions 

 calculated to generate its maximum antirachitic activity (although ac- 

 cording to Rosenheim and Webster it contained probably less than 10 

 per cent of vitamin D), Coward (1928c) found that feeding 0.00002 

 milligram daily resulted in -\ — (- heaUng, comparable to "positive" 

 rating given by Steenbock, in rats made rachitic by Steenbock's diet No. 

 2965. Thus for the 10 days' test, 2 X 10"* milligram or 2 X 10"' gram 

 of the activated material was required. The amount of vitamin D actually 

 fed, then, was approximately 2 X 10"® gram, an amount which con- 

 firms the estimation of Fosbinder, Daniels and Steenbock (1928) of the 

 quantity of vitamin D necessary to produce renewed deposition of 

 calcium in the bones of rachitic rats. 



Inasmuch as Coward found a certain degree of healing when half 

 or even one- fourth of this amount was fed, she suggested that the line 

 test is suitable for detecting still smaller quantities. 



Poulsson and Lovenskiold (1928) recommend taking a skiagram of 

 the left knee joint at the beginning and end of the test period, in experi- 

 ments conducted similarly to Steenbock's line test, and base estimates 

 of the antirachitic value of supplementary material upon changes in the 

 appearance of the X-ray pictures taken before and after administration 

 of the materials to be tested, rather than upon the "line test." 



Knudson and Moore ( 1929) have used radiographic studies parallel 



