August 13, 1920] 



SCIENCE 



157 



tending over more than a year, the following on a study of some 500 rats that were fed on 

 nimibers of young have been obtained. definite synthetic rations. 



The non-crossover classes have consist- In our laboratory we have had occasion to 



ently been in excess of the crossover classes, feed white, and black and white rats on various 

 In a total of 83 young, 32 have shown cross- synthetic rations and in going over our records 

 over groupings of the two pairs of characters, we have compiled data bearing upon the pre- 

 and 51 have shown non-crossover groupings. valence of xerophthalmia in relation to the 

 This is 38.5 per cent, crossovers, an indicated known presence or absence of the fat-soluble 

 linkage strength of 23 on a scale of 100. A. These results are given in the table below. 



In a previous paper I have shown that Eng- 

 lish pattern is allelomorphic with Dutch pat- 

 tern, or very closely linked with it. If Eng- 

 lish is linked with dilution, Dutch also must 

 be linked with dilution. Attention should 

 now be turned to the question whether other 

 characters of rabbits belong to this same link- 

 age group, and whether other linkage groups y, . ,, , j. r -,nn j. r^ a mn 

 , , ' , . ... a a f j^ jg gggjj ^^g^^ ^^^ q£ J22 rats. Group A, 120 

 can be detected m rabbits. j. ^, „„ o . ■, -, 



ot them or 98.3 per cent, showed sooner or 



W. hi. Castle later positive signs of xerophthalmia, and that 



BussET Institution, .s^^hen the fat-soluble A vitamine was present, 



July 24, 1920 ^ .^^j^j^ ^^ without the water-soluble B (Groups 



B and C), none of the 319 rats showed evi- 

 dence of this eye ailment. All the rats were 

 fed individually in practically every case. 

 They were kept in metal cages, without any 

 bedding, which were provided with a special 

 removable wire screen floor. The cages, and 

 the food and water cups were always disin- 

 fected once or twice a week. The sanitary 

 conditions were, therefore, good. The same 

 assistants handled and fed all the rats so that 

 the attention given them was the same for all 

 and the possibilities of infection from this 

 source was uniform. 



It would seem to us that if xerophthalmia 

 was primarily infectious and due to the poor 

 hygienic conditions, that some of the rats in 

 Groups B and C would certainly have devel- 

 oped it. Further, repeated attempts were 

 made to transmit the disease by using sterile 

 threads of gauze, passing them cautiously 

 over the edge of the lids of the sore eyes, and 

 then carefully inoculating the eyes of the 

 other rats. These tests were negative, as were 

 the controls. This was fairly good evidence 

 that the disease could not be transmitted by 

 this means. 



Treatment of advanced cases of sore eyes 

 with a saturated boric acid and also with a 



THE FAT-SOLUBLE A VITAMINE AND 

 XEROPHTHALMIA! 



It is generally admitted by those who have 

 conducted feeding experiments with rats that 

 although the essential dietary factors for 

 growth, including the so-called water-soluble 

 B, are present, the animals will not grow to 

 maturity with out the fat-soluble A. The 

 work of Osborne and Mendel, McCollum and 

 associates, Drummond, Steenbock and asso- 

 ciates, and others give abundant evidence of 

 this fact. All investigators are not in accord, 

 however, that a positive lack of the fat-soluble 

 A is the direct cause of the eye condition in 

 the rat which McCollum- designated as 

 xerophthalmia, some considering this disease 

 to be primarily infectious. 



Bulley^ has recently taken the most definite 

 stand that this eye condition is not due to a 

 dietary deficiency but primarily to infection, 

 resulting from poor hygienic surroundings 

 and uncleanliness. She based her conclusions 



1 Read TDef ore the American Chemical Society, 

 St. Louis, April, 1920. 



2 McCollum, E. v., and Simmonds, N., Jour. Biol. 

 Chem., 1917, XXXII., 29. 



3 BuUey, E. C, Biochem. Jour., 1919, XIII., 103. 



