650 



SCIENCE 



[Vol. LVI, No. UjS- 



constant use of structural formulas. With such 

 practise the study of two chapiters of organic 

 chemistry is not appalling. 



A library shelf, easily accessible and espe- 

 cially selected for students of general chemis- 

 try, pays goods dividends. Other tests, books 

 on the applications and special advertising 

 pamphlets should fill tOiis shelf. Not all will 

 read but those who do aa-e the ones who take 

 advanced chemistry. 



Stress must be placed on equilibrium, early 

 and late, on solutions, on that fascinating 

 chapter about the periodic system, on the 

 hydrocarbons and their derivations and such 

 other topics as appeal strongly to the teacher. 



An informal talk with each student or a 

 wi'itten test on entrance will indicate that some 

 who have had high school ohemistry will do 

 better in the class with those who had none. 

 Since high schools vary widelj' in quality of 

 instruction in chemistry (as do colleges also) 

 the mere name of preparatory chemistry 

 should not be accepted without some investi- 

 gation. Usually the record of the school is 

 sufficient evidence. 



Hahet N. Holmes 



Obeehn College, 

 Oberlin, Ohio 



ON THE EXISTENCE OF A HITHERTO 

 UNRECOGNIZED DIETARY FAC- 

 TOR ESSENTIAL FOR RE- 

 PRODUCTION! 



The fact has been abundantly demonstraited 

 tiha't rats may be reared on a dietary regime 

 consisting of "purified" protein, fat and carbo- 

 hydi^ate to which an appropriate salt mixture 

 and adequate doses of the groAflth vitamines 

 Tat Soluble A and Water Soluble B have been 



1 University of California, aided by the Dairy 

 Division of the Bureau of Animal Industry of 

 the United States Department of Agriculture, the 

 Committee for Research on Sex Problems of the 

 National Research Council and the California 

 Central Creameries. The writers desire also to 

 express their especial thanks to Mr. C. E. Gray, 

 of San Francisco, and Dr. C. W. Larson, of 

 Washington. 



added. We have employed a ration of casein 

 (18), cornstarch (54) and lard (15) to which 

 Dutterfat (9) and salts (4) are added, the ani- 

 mals receiving separately and daily .4 gram, 

 each of dried whole yeasit. 



Such animals are siterUe. They are chiefly 

 so in the fii'st generation and wholly so in tihe 

 next succeeding one. The sterility of dietary 

 origin yields a highly characteristic picture. 

 Animals suffering from it do not differ so pro- 

 foundly from normal ones in their ovarian 

 funcldon as they do in placental behavior. Ap- 

 proximately the same number of Graafian fol- 

 licles maiture and rupture per ovulation and 

 the ova are fentiHzed and implanted. The 

 placentcB are abnonnal. They may persist al- 

 most throughout; gestaition but show as early 

 as the second day of their e^talbliShment begin- 

 ning blood extravasations wMch increase in ex- 

 tent. Eesorption invariably overtakes the pro- 

 dueits of conception. 



Natural foodstuffs contain a substance, X, 

 whidh prevents such a sterility or whieih cui-es- 

 'the disorder occasioned iby the purified dietary 

 i-egime. We have thus been able to witness a. 

 comparatively sudden reStora;tion of fertility 

 to animals of proven sterility, and whose con- 

 trols continued stei-ile, by the administration: 

 of fresh green leaves of lettuce. Even the dried 

 teaves of alfalfa appear to possess a similar 

 potency. The proven efficacy of leaves invites 

 inquiry into the certainty of segregutdon of 

 the new dietary factor from AdtamLnes A and 

 C. As regards A, it is conceivable that amounts 

 of A adequate for normal growth, freedom 

 from eye disease and, indeed, Aagorous health, 

 might sitill be inadequate for the reproductive 

 function. Such a -conception is apparently 

 strengthened by the reappearance of fertdlity- 

 which we have ■discovei'ed to take place when 

 the butiterfat. quota in the above diet is in- 

 creased so as to constitute 24 per cent, by- 

 weight.- A sufficient answer to this conception,, 

 howe^'ei-, is afforded Iby our demonstration that 

 in some dietaries i-eproduotion may be un- 

 hindered when the A content is lower than in 



2 Drummond (Biocliem. Jour., xiii, 77) has, for- 

 instance, reported two generations of animals; 

 reared on 20 per cent, butter in this diet. 



