Mat 25, 1917] 



SCIENCE 



507 



reduced, but it minimizes the possibilities of 

 adding excessive quantities of protective col- 

 loids which might stabilize the cuprous oxide 

 in its finely divided form. Finally, in doubt- 

 ful cases, a dilution of the reaction mixture is 

 always to be tried. By this method there is 

 avoided not only excessive concentration of 

 the reducing body itself, but through adequate 

 dilution, both those protective colloids which 

 may be added from without, or those which 

 may be formed in the reaction mixture itself 

 are likely to be diluted to a point where their 

 effect in stabilizing the cuprous oxide in its 

 finely divided form is largely lost. 



While working on the reduction of Feh- 

 ling's solution by formaldehyde, we encoun- 

 tered a series of reactions which, while largely 

 familiar to the physical chemists since Bredig's 

 classical studies on the inorganic ferments, are 

 somewhat new in their sum total; and since 

 the reactions are strikingly like those ob- 

 served in biological material, we have used 

 them to elucidate the nature of such biological 

 reactions for our students. 



Formaldehyde reduces a Pehling's solution 

 not only to the ordinary cuprous oxide, but to 

 the metallic copper. The copper comes down 

 in colloid form, but as this happens, a second 

 reaction ensues in which the metallic copper 

 acts upon the formaldehyde and decomposes it 

 with the liberation of hydrogen. The libera- 

 tion of hydrogen continues for hours, until 

 either all the formaldehyde has been decom- 

 posed or all the copper salt has been reduced. 



We use this reaction as a biological analogue 

 illustrating the formation of an enzyme (the 

 reduced copper) from a series of simple 

 "dead" materials (alkali, salts, carbohydrate). 

 From another point of view we may say that 

 the formaldehyde poisons or acts as a toxin 

 upon the Fehling's solution. Against this the 

 reaction mixture produces an antitoxin (the 

 metallic copper). 



The reaction may also be used to illustrate 

 the action of diilerent enzymatic poisons. 

 Potassium cyanide, for example, when added 

 to the Fehling's solution will not only prevent 



its reduction by the formaldehyde but, added 

 after the reduction has been initiated, will in- 

 hibit or stop further reduction and liberation 

 of hydrogen. 



As emphasized by Hoppe-Seyler, the produc- 

 tion of nascent hydrogen is held to be essential 

 in the chemistry of respiration. But depend- 

 ing upon whether this production of hydrogen 

 in a biological oxidation mixture occurs in the 

 presence or in the absence of oxygen, totally 

 different effects (as an oxidation in the one 

 case or a reduction in the other) may be 

 brought about. The same is true of the chem- 

 istry of a Fehling's solution when reduced by 

 formaldehyde. 



If a substance like methylene blue or phenol- 

 sulphonephthalein is added to the reaction 

 mixture, these dyes are left untouched or are 

 deoxidized, depending upon whether the reac- 

 tion mixture is kept in a flat dish exposed to 

 oxygen or in a tall tube from which oxygen is 

 largely excluded. In other words, the first dye 

 behaves just as in the classical experiments of 

 Paul Ehrlich upon tissue oxidations; the phe- 

 nolsulphonephthalein acts as in the experi- 

 ments of E. C. Kendall. Phenolsulphoneph- 

 thalein suffers reduction in the body whenever 

 oxygen is absent while it is left untouched 

 when this is not the case. 



A detailed account of these experiments has 

 been sent to the Kolloid-Z eitsclirift for publi- 

 cation. Martin H. Fischer, 

 Marian O. Hooker 



EiCHBEKQ Laboratory op Physiology, 

 University op Cincinnati, 

 March 13, 1917 



THE OIL CONTENT OF COTTON SEED AN 



ACCURATE BASIS FOR COMMERCIAL 



STANDARDIZATION 



As a result of four years' work by the author, 

 three of which are shown in the table below, 

 and based on more than 500 determinations 

 in the cotton industry laboratory of the 

 Georgia State College of Agriculture, it was 

 found that the oil content of cotton seed is an 

 inherent characteristic of the variety, and 

 that the percentage of oil in any variety can 

 be increased by selection with no correspond- 

 ing loss of other desirable qualities. Al- 



