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Journal of Experimental Biology 31,573-581 (1954)
Published by Company of Biologists 1954

The Structure of the Yolk of the Hen's Egg, Investigated by means of its Permeability to ⁸²Br

D. M. MAURICE ¹ and A. FIDANZA ¹

¹ Institute of General Physiology, Rome

1. ⁸²Br was mixed with the white of hen's eggs maintained at 1° C., and its concentration in the yolk and white measured after experimental periods ranging from 5 min. to 200 hr. In some cases the distribution of ⁸²Br in the yolk was determined.

2. From 5 hr. onwards the concentration in the yolk increased at a constant rate reaching on the average 2.5% of that in the white after 200 hr. This suggested that the penetration was opposed by an external membrane of low permeability (7 x 10^-5 cm./hr.).

3. Before 5 hr. the amount of ⁸²Br in the yolk was in excess of that predicted by this mechanism. This did not appear to result from contamination from the white and suggested that there was a layer of yolk external to the resistive external mem brane and therefore this was not the vitelline membrane.

4. Even after 100-200 hr. most of the 82Br which had penetrated remained in the superficial layers of the yolk. This showed that there was also a resistance to its penetration in the mass of the yolk itself.

5. The bearing of this evidence on the structure of the yolk is discussed.

Note:

Now at the Ophthalmological Research Unit, Institute of Ophthalmology, Judd Street, London.