September 30, 1921] 



SCIENCE 



293 



but parallel. This model, however, is unstable, 

 for the ionizing potential computed by apply- 

 ing the quantum theory, comes out negative. 

 Another objection to this model is that the 

 magnetic moment is not zero. (3) In the 

 semi-circular model each electron is assumed 

 to oscillate back and forth along an approxi- 

 mately semi-circular path in accordance with 

 classical mechanics, each being brought to 

 rest at each end of its path by the repulsion 

 of the other. Assuming the maximum angu- 

 lar momentum of each electron equal to 7i/27r 

 the absolute dimensions come out such as to 

 give a total energy 0.9618 times that of the 

 Bohr model, and the computed ionizing po- 

 tential, 25.62 volts, agrees closely with the 

 experimental value. The magnetic moment is 

 zero. 



Application of the quantum theory to 

 coupled electrons. — The success of the semi- 

 circular model of helium suggests that in the 

 case of coupled electrons the quantum theory 

 should be applied not to the momentum of the 

 individual electrons according to the relation 

 fpdq =' h/^TT, but rather to the momentum 

 which by being relayed from one electron to 

 another, passes in each direction around the 

 nucleus. 



4. Studies on inbreeding. IV. Effects of in- 

 breeding on the growth and variability in 

 body weight of the: albino rat. Helen D. 

 King; Jour. Exp. Zool., 29, No. 1 (1919). 



ABSTRACT 



Effects of inbreeding on the growth and 

 variability in body weight of the albino rat. — 

 In continuation of previous work, data are 

 given concerning over 600 rats belonging to 

 the sixteenth to twenty-fifth generations of a 

 strain bred brother to sister from the same 

 litter only. Allowing for the effect of certain 

 unfavorable conditions, determined by control 

 rats, the results confirm previous conclusions 

 and show that close inbreeding continued for 

 25 generations has not produced any deteriora- 

 tion in the stock as regards the growth curve, 

 the body weight, the variability of body weight 

 for various ages, and the relative behavior of 



the sexes in these respects. Selected rats were 

 used as the parents of each generation. If 

 there is any tendency to deterioration it was 

 counteracted in these experiments by the se- 

 lection employed. 



Effect of nutrition on the growth and varia- 

 bility in body weight of the albino rat. — ^Rats 

 are particularly sensitive to food conditions. 

 Alfalfa, cottonseed and linseed meal were 

 found to be injurious. A change from a satis- 

 factory diet to one less suitable resulted in a 

 marked increase in variability of body weight 

 both for inbred and stock rats. 



Sex ratio in the albino rat. — By selection 

 the inbred strain has been separated into two 

 lines, one with a high, the other with a low> 

 sex ratio; but the effect of selection seems to- 

 be limited. The two strains are alike in body- 

 weight, growth curve and variability of body 

 weight. 



It will be noticed that each of the one or 

 more paragraphs of each abstract begins with 

 an italicized paragraph title. In some cases 

 words or phrases within a paragraph are also 

 italicized. This is not done for emphasis but 

 to associate them with the paragraph titles 

 which they supplement and complete. Para- 

 graph titles and italicized words and phrases 

 will collectively be called subtitles. If the 

 reader will run through the sample abstracts, 

 skipping all but these italicized subtitles, he 

 will get in each case a descriptive index of 

 the information in the article. For example: 



ABSTRACT NO. 1 



Atomic weight of iodine. 



Pentoxide method. 



Determinations. 

 Iodine pentoxide. 



Preparation, purification. 



Decomposition with heat. 

 Preparation of pure iodine. 

 Occlusion of oxygen by glass, porcelain and 



copper. 



ABSTRACT NO. 3 



Helium atom models. 



(1) Bohr's model. 



(2) Double circle model. 



(3) Semi-circular model. 



