Dr. Steenbock was the first to suggest a relationship between pigments and vitamine A: wherever there were pigments, particularly such as are found in abundance in the plant world, there was vitamine A. He even went so far as to suggest that the two - pigment and vitamine A - were possibly identical. This view has been very strenuously opposed by a number of investigators, and if one is to judge by one of his latest papers, Dr. Steenbock himself has modified these views.

Dr. Drummond, among others, put the pigment-vitamine A idea to a thorough test. He tried the following animal and vegetable oils, the vitamine content of which is roughly given, based on butter as 10: cod liver oil 10;1 dog-body fat, 6-7; beef fat,

1 This is undoubtedly much too low, as the reference to Dr. Zilva's work in a previous section will show. If the sample of cod liver oil is crude - one that has not been refined, perhaps 250 would be nearer the mark than 10; on the other hand, a specially refined cod liver oil is probably not much higher than 10. Unfortunately for all concerned, the type of cod liver oil - its origin, how prepared, etc. - used is never referred to.

6-8; mutton fat, 2; pig fat, 1; lard, 0; horse fat, 6-8; linseed oil, 1-2; hardened linseed oil, 0; palm oil, 3-4; maize oil, 2-3; cottonseed oil, 1; hardened cottonseed oil, 0; peanut oil, 0; olive oil, 0-1. These results show that though inferior to the majority of animal fats, many vegetable fats do contain appreciable quantities of vitamine A, which is contrary to earlier findings by various authors. No connection between pigment and vitamine contents was found. "Our experiments make it clear that unless we accept the suggestion advanced by Steen-bock, of the existence of a leuco compound (a colorless precurser) of the pigment, to account for the exceptions, his theory fails to hold good. (The authors arrived at this conclusion by extracting the amounts of carotin and xanthophyll - the two pigments concerned - and comparing such results with the corresponding vitamine content. For example, though dog-body fat showed a vitamine content of 6-7, there were no pigments present.)

Professor Palmer, of the University of Minnesota, presents evidence in support of Dr. Drum-mond's work. He obtained normal growth and reproduction in albino rats, a species of animal in which there is complete absence of (carotinoid) pigments, with ewe milk fat and pigment (carotinoid) - free egg yolk as the sole sources of vitamine A.

Another instructive experiment is that due to Miss Marjary Stephenson, of the Biochemical Laboratory, Cambridge, England. 300 grams (about 30 grams to the ounce) of filtered butter were dissolved in one liter (about a quart) of light petroleum and about 4 grams of fine birch charcoal were added. This was shaken for two hours in the shaking machine; filtered, and retreated with charcoal. A butter fat free from color was obtained. The petroleum was now distilled off under reduced pressure; the resulting butter was white and resembled lard in appearance. Two sets of eight rats were put on an experimental diet (starch, sugar, purified casein, salt mixture, fat-free alcoholic extract of yeast and a little lemon juice), one set getting the decolorized butter fat, and the other the untreated fat. Perfect growth was maintained in both sets for 8 weeks, after which the experiment was discontinued. Hence it may be concluded that the removal of the coloring matter of butter does not affect the vitamine content. (References: H. Steenbock, Science, volume 50, page 352, 1919; H. Steenbock and P. W. Boutwell, Journal of Biological Chemistry, volume 41, pages 81 and 163, 1920; H. Steenbock and E. G. Gross, Journal of Biological Chemistry, volume 41, page 149, 1920; L. S. Palmer, Science, volume 50, page 501, 1919; L. S. Palmer and C. Kennedy, Journal of Biological Chemistry, volume 46, pages 559,1921; J. C. Drum-mond and K. H. Coward, Biochemical Journal, volume 14, page 668, 1920; M. Stephenson, Biochemical Journal, volume 14, page 715, 1920; R. A. Dutcher, Journal of Industrial and Engineering Chemistry, volume 13, page 1102, 1921; H. Steenbock, M. T. Sell and M. V. Buell, Journal of Biological Chemistry, volume 47, page 89, 1921.)