Feeding Experiments with Fat-free Food Mixtures. 73 



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Feeding experiments with fat-free food mixtures. 

 By THOMAS B. OSBORNE and LAFAYETTE B. MENDEL. 



[From the Laboratory of the Connecticut Agricultural Experiment 

 Station, and the Sheffield Laboratory of Physiological Chemistry 

 in Yale University, New Haven, Connecticut.] 



[With the cooperation of the Carnegie Institution of Washington.] 



The question as to whether fats are, like proteins and carbo- 

 hydrates, in some measure indispensable components of the diet 

 has never been adequately determined. Stepp 1 has lately main- 

 tained that the so-called "lipoids," in distinction from true fats, 

 are necessary for adequate nutrition. His experiments were con- 

 ducted with mice. Following the methods employed by the 

 writers 2 it has been possible to induce rats to grow at a normal 

 rate with food mixtures containing only purified proteins, carbo- 

 hydrates and inorganic salts. The problems suggested by the 

 possibilities of this method of investigation are obvious. 



53 (662) 



The masking of a Mendelian result by the influence 

 of the environment. 



By T. H. Morgan. 



[From the Department of Zoology, Columbia University.] 



As reported (Oct., 191 1) a mutant of Drosophila appeared with 

 a dominant sex-linked character, viz., abnormal abdomen. Typical 

 Mendelian ratios are found in the F2 offspring if an abundance 

 of food and of moisture is present. As the culture grows older 

 the flies that emerge later gradually change over to the normal 

 type. As a result the Mendelian ratio completely disappears 

 from the surface phenomena. That Mendelian inheritance has 

 actually occurred, but is temporarily masked, is shown by testing 

 the F 2 flies, when the expected number is found (under wet 



1 Stepp. Zeitschrift fir Biologie, 1911, LVII, p. 135. 



* Osborne, T. B., and L. B. Mendel, "Feeding Experiments with Isolated Food- 

 Substances," Carnegie Institution of Washington, Publication 156, 1911. 



