32 SCIENCE PROGRESS 



were raised by a mother on a diet of white bread alone. This 

 latter observation is rather unexpected and quite contrary to 

 the writer's experience, who has also seen many cases of failure 

 to raise rat litters accompanied by symptoms similar to those 

 described by Hartwell, but only when the mother is receiving 

 a ration inadequate in the vitamin B, Apparently this 

 possible explanation was also in Hartwell's mind, for she has 

 since tested the effect of adding this dietary unit (vitamin B) 

 to the mother's diet {Biochem. J., 1922, 16, 78). Actually this 

 addition did enable the litters to be raised, although she hesitates 

 to ascribe the general failure to vitamin deficiency. Many of 

 her experiments, however, require repeating, and other possible 

 causes of the death of the young should be carefully examined 

 before the toxic effect of the protein which she emphasises is 

 accepted on the evidence submitted. 



Testing for the Presence of Vitamins. — ^A necessary fore- 

 runner of any such reconsideration of the regulations for milk 

 control as is referred to above is, however, the discovery of more 

 accurate methods of estimating the amount of the vitamins 

 present in a foodstuff than are available at present. No 

 chemical or physical methods of any approved value have yet 

 been advanced. The yeast test for the quantitative estimation 

 of vitamin B at first advanced by Williams (/. Biol. Chem., 

 1 91 9, 38, 465) and still supported by several workers has been 

 shown to be untrustworthy by Souza and McCollum (/. Biol. 

 Chem., 1920, 44, 113), and by Nelson Fulmer and Cessna (/. 

 Biol. Chem., 1921, 46, yy) : the latter having demonstrated a 

 fundamental error in the method in showing that yeast grown 

 in pure culture can synthesise vitamin B. 



The accuracy of the biological test used for the testing of 

 foods for the vitamin A has been considerably improved by the 

 technique described by Zilva and Muira {Biochem. J., 1921, 15, 

 654). The writer can vouch for the consistent results that may 

 be obtained by closety following this technique. 



The usual method of testing quantitatively for vitamin C 

 is laborious and of doubtful accuracy, so that confirmation of 

 the work of Bezessonoff {Compt. rend., 192 1, 173, 466), who finds 

 the antiscorbutic factor to be associated with the power to give 

 a characteristic coloration with a modification of the Folin- 

 Denis phenol reagent, will be hopefully awaited, 



A summary of the methods employed for the testing of food 

 products for the three vitamins was recently presented to the 

 Society of Public Analysts by Drummond and Watson {Analyst, 

 1922, May). 



Chemotropism. — A very interesting biochemical study of 

 which the results may be of great practical importance is 

 described by Harington {Biochem. /., 1921, 15, 736). He has 



