114 THE VITAMINS 



lack of food intake records complicates their interpretation while the 

 large losses of vitamin as soon as precipitation was resorted to find 

 no parallel in analogous work with the antineuritic substance." 



"The ready adsorption of water-soluble B by precipitates of all de- 

 scriptions postulated by Drummond, in explaining the large losses during 

 chemical manipulation, does not seem to be a property of the anti- 

 neuritic vitamin. Thus, Emmett and McKim (1917) show that while 

 this vitamin is adsorbed by fuller's earth and Lloyd's reagent it is 

 not adsorbed by the kieselguhrs or infusorial earths, indicating a selec- 

 tive adsorption by the former. Being readily dialyzable, there seems 

 to be no compelling reason for believing it to be indiscriminately ad- 

 sorbed by precipitates of all kinds." 



With regard to the stability of the two vitamins, evidence was cited 

 that both are stable to acids and to even concentrated alkalies at room 

 temperature. At the boiling temperature the antineuritic vitamin ap- 

 peared to be rapidly destroyed by alkaU (Steenbock, 1917), while the 

 growth-promoting vitamin was more stable although the results with 

 alkalies were somewhat confusing (Drummond, 1917; Osborne, Wake- 

 man and Ferry, 1919; McCollum and Simmonds, 1918; and Daniels 

 and McClurg, 1919). 



As to stability toward heat, the evidence was also conflicting for 

 temperatures above 120° C, although a greater stability of the growth- 

 promoting vitamin was again indicated. (Chick and Hume, 1917b; Mc- 

 Collum and Davis, 1915c; McCollum, Simmonds and Pitz, 1917; 

 Daniels and McClurg, 1915; and Drummond, 1917.) 



Mitchell concluded that there seemed to be very good reason for 

 doubting the identity of the two vitamins but that in settling the ques- 

 tion definitely there was need of quantitative experiments in which the 

 same materials are tested for their growth-promoting and antineuritic 

 properties. 



The following year Emmett and Euros (1920) reported an investi- 

 gation of this kind, the results of which cast further doubt upon the 

 then usual assumption that the antineuritic and water-soluble growth- 

 promoting vitamin were identical. The particular phase of the problem 

 considered was the stability of the water-soluble vitamin to heat. A 

 compilation of the available data on this point, with some considera- 

 tion of the possibility that the amount of ration consumed might carry 

 an excess of the vitamin beyond minimum requirements and so mask 

 partial destruction, showed that the antineuritic and the growth-pro- 

 moting vitamins, as measured by polyneuritic pigeons and young rats 

 respectively, were fairly stable at temperatures around 100° to 105° C, 



