830 



BIOPHYSICAL PHENOMENA 



[PT. Ill 



^^°^^ 



^^\. 8 Unincubated 



his part, that the specific resistance of the interior of the egg was 

 about 90 ohms per c.c. or 3-6 times that of sea water, and that 

 the impedance of the surface of the egg is probably similar to that 

 of a "polarisation capacity". On these values membrane formation 

 and cell division seemed to be without effect. 



The electrical resistance of the constituents of the hen's egg has 

 been studied by Bellini. The figures he obtained are shown in Fig. 203. 

 If the egg is not incubated at all, the resistance of the yolk and the 

 white remains quite constant even over a much longer period than 

 that represented on the graph. 



If, however, the egg is placed at ^— $. Bellini 



37°, the resistance of the yolk 

 augments until the 6th day, 

 after which it declines to its 

 initial value. That of the white 

 was not followed by Bellini after 

 the 8th day, but rose quickly 

 up to that point. It is not easy 

 to interpret these results, but 

 presumably they indicate a de- 

 mobilisation of free electrolytes 

 throughout the extra-embryo- 

 nic part of the egg during the 

 I St week of development. Prac- 

 tically nothing is known about 

 the behaviour of the inorganic 

 constituents of the yolk and the 

 white during this time^. The fact that the embryonic body is at this stage 

 more rich in ash, and therefore probably in electrolytes, than at any 

 other stage, though unknown to Bellini, may have some bearing on the 

 question, but the embryo is now so small in relation to the yolk and 

 white that it is doubtful whether its absorption of electrolytes could 

 account for the changes in electrical conductivity of the rest of the egg. 



According to Fiirth the dielectric constant of yolk in the hen's 

 egg is 60 and that of white 68. 



Other phenomena were discovered by Hermann & von Gendre, 

 who found in 1885 that the developing chick embryo is always 

 positive to the yolk and the white. At 80 hours' development, there 



^ But see Fig. 405 and Section 13' i. 



m 



$ Incubated &, developed 

 9 " nob » 



o Unincubated 



Unincubated 



frw] 



Level of electrical resistance of 

 adult blood serum&.amniotic fluid 



5 Days 

 Fig. 203. 



