THE GROWTH-PROMOTING HORMONE 



with a "standard" preparation available to different labora- 

 tories so that potency could be stated in terms of a standard 

 preparation. 



The only attempts to determine the relationship between 

 the dose and the response in normal rats were those of van 

 Dyke and Wallen-Lawrence (1930) and Evans, Meyer, and 

 Simpson (1933). The former workers gave different doses of 

 one preparation, in proportion to the body-weight, in differ- 

 ent orders to a group of thirty-six adult rats most but not all 

 of which were female. The short-term (injection for three 

 successive days) method was used with the following results 

 (given in the order of administration, the relative dose and 

 the percentage increase in weight being indicated in each pair 

 of figures): 2.0:3.58; 1:1.09; 1.5:3.45; 2-3:3-2i; 1.25:2.34; 

 1.25:2.18; and 4:4.14. Seventeen per cent of the animals re- 

 sponded only to the largest dose. Evans, Meyer, and Simp- 

 son used four to six adult female rats for each dose, which was 

 given seventeen times over a period of 20 days. In studying 

 the relationship between the relative dose and the gain in 

 weight (from 15-20 g. to 60-70 g.) produced by three differ- 

 ent preparations, they found that the logarithm of the change 

 in weight was proportional to the logarithm of the change in 

 dose. In the case of one preparation log jy = 0.48 log;^+i-22, 

 in which y is the change in weight expressed in grams and x is 

 the relative dose expressed as an arbitrary unit. This, how- 

 ever, is not a general expression; in the cases of the different 

 preparations, the intercept, of course, varied. More impor- 

 tant is the fact that the slope varied from 0.48 in the case just 

 cited to about 0.26 in the best of the other experiments. In 

 other words, two different preparations do not produce the 

 same proportional change in the logarithm of the change in 

 weight in relation to the logarithm of the change in dose. In 

 the data of Evans, Meyer, and Simpson is an example of the 

 assay of one preparation administered in different doses 

 (preparation K 18, smallest dose, 11.4 mg. given here as a 



[105] 



