820 BIOPHYSICAL PHENOMENA [pt. iii 



The frequent occurrence of broken yolks in stored eggs shows that 

 the water current eventually overcomes the resistance. Rice & Young 

 estimated the osmotic pressure and the refractive index in the eggs 

 of various kinds of hen, in order to assess the relative intensity of 

 the water current in different eggs, but there were no perceptible 

 variations from the mean. Kamei's data are in good agreement with 

 those of Bialascewicz. 



Table 92. 



Osmotic pressure Refractive index at 



A (°) 20° C. 



White Yolk White Yolk Investigators 



White Leghorn pullet -0-435 -0-580 1-3565 i-4i75 Rice & Young 



White Leghorn hen -0-442 -o-6oi 1*3560 1-4188 „ 



White Wyandotte -0-428 -0-576 1-3546 i'4i83 " 



Barred Plymouth Rock -0-436 -0-602 i-3550 1-4192 



Rhode Island Red -0-446 -0-575 i'3568 1-4185 ,, 



Various attempts have been made to gain some further information 

 about the nature of the osmotically active substances in the yolk, 

 as, for instance, Bialascewicz's own work on the electrolyte content 

 of bird and fish egg-yolks, already mentioned in Section i • 1 6. In 1 902 

 Stewart showed that hen's egg-yolk is a very much poorer conductor 

 of electricity than a solution of its salts made up to the same volume. 

 McClendon in 19 10 examined the electrical conductivity of centri- 

 fuged suspensions of yolk, one poor in lipoid-protein yolk granules, 

 the other rich in them. There was a sHght difference between the 

 two, the granule-poor suspension conducting rather better than the 

 granule-rich one. Dilution, which breaks up ion-colloid compounds, 

 made the conductivity of both suspensions decrease, a paradoxical 

 result which McClendon was unable to explain. 



5-7. Specific Gravity 



The subject of osmotic pressure during embryonic life leads 

 naturally to the discussion of specific gravity, many measurements 

 of which have been made by marine biologists interested in the eggs 

 of plankton. Here the question is complicated by the fact that the 

 relative quantity of fats and oils, substances which have Httle or no 

 osmotic activity, has importance in deciding whether an egg shall 

 float or sink. The facts have been reviewed by Strodtmann and by 

 Russell. 



