246 CORTEX 



chief difficulty of obtaining such evidence, in the author's ex- 

 perience, lies in the extremely small yield of the crystalline 

 products which are obtained from the glands, as is also the 

 case in the isolation of other hormones. It requires the extrac- 

 tion of about 200 kilograms of fresh glands to yield approxi- 

 mately one gram of the crude hormone. To one having the 

 facilities for obtaining this material the eventual isolation of 

 the hormone should not be difficult. The non-protein nature 

 of the hormone should make it amenable to crystallization and 

 its reactivity should permit the formation of easily crystalliz- 

 able derivatives. 



The results of chemical investigations based on the use of 

 extracts are always uncertain. Only results obtained on pure 

 crystalline products are acceptable as truly characterizing the 

 hormone. The presence of any impurities will always vitiate 

 the validity of results obtained on hetereogeneous extracts. 

 We shall not therefore enter into great detail in an enumeration 

 of such chemical properties of the cortical hormone as have 

 hitherto been described. Several properties of the hormone 

 which are of importance should, however, be mentioned here. 

 The hormone is not a protein. This is demonstrated by its 

 solubility relations and its effectiveness when administered 

 orally. The purest extracts obtained by the author have 

 always been readily soluble in polar liquids (ethyl or methyl 

 alcohol), less so in non-polar solvents (ether or benzene). The 

 presence of extraneous lipids alters these solubility relation- 

 ships so that we find impure extracts to be readily soluble in 

 ether and insoluble in water, whereas the reverse is true of the 

 purer preparations. This apparent paradox is frequently 

 observed in dealing with biological mixtures. The lipids of 

 the adrenal can tenaciously hold the hormone and determine 

 its apparent solubility. Thus the hormone may be extracted 

 from its crude aqueous solution by benzene. On the other 

 hand, benzene or ether will not readily extract the purified 

 hormone from aqueous solution, for when purified it is no 

 longer being held by extraneous lipids. 



