262 CORTEX 



same dose of the hormone. In Figure 16 are reproduced the 

 average growth curves of groups of six adrenalectomized rats. 

 One group of six rats was given an intraperitoneal injection of a 

 purified extract. The food of a second group of six animals was 

 mixed with an amount of the extract exactly equal to that 

 injected into the first group. As is evident from Figure 16 the 

 oral form of therapy gave a markedly superior therapeutic 

 effect as compared to the injection of an equal amount of the 

 same extract. 



ACCURACY OF THE RAT ASSAY METHOD 



One can assay preparations of the adrenal cortex by the rat 

 method with a degree of accuracy which is unusually good for a 

 biological method. Obviously, for the best results, certain 

 rigid conditions must be maintained. The animals used should 

 be uniform in quality and in good health. They should be 

 maintained under constant conditions at a moderate and 

 uniform room temperature (25°C). 



One would hardly expect different workers under varying 

 laboratory conditions and using diverse operative techniques, 

 to obtain perfectly identical results. To render the results of 

 different workers comparable it would be necessary to have 

 some standard as a unit of comparison. Unfortunately, such a 

 standard is not available at present. However, the white rat 

 is relatively uniform in its reactions and by using a standard- 

 ized technique, comparable results should be obtainable by 

 different workers. In the author's experience, the rat method 

 of assay as outlined above is reproducible to within ± ten 

 per cent. 



As shown in Figure 16, the administration of an excess of 

 sodium chloride and bicarbonate in the diet does not permit 

 normal growth in young adrenalectomized rats. The same is 

 true of the administration of Ringer's solution in place of 

 drinking water, or the injection of large amounts of physio- 

 logical saline or Ringer's solutions. Only when the operation 



