Structure and Permeability of the Chorion in the Silkworm Egg

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  • 家蚕卵殼の構造と透過性
  • カサン ランカク ノ コウゾウ ト トウカセイ

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Abstract

1. In ordinary paraffin and free-hand sections stained with haematoxylin seven layers may be discriminated in the chorion of the silkworm egg. Superficial two layers, the outermost stained and the next unstained, may be referred to the outer chorion of other authors. The endochorion is made up of five layers. They are from outside a scarcely stained layer provided with many vertical lines which are supposed to be pore canals, a thin laminated layer likewise unstained, a heavily stainable thin layer, an unstained thin layer, and an innermost good stained thin layer (Fig. 1).<br>2. Methylene blue does not enter into the yolk of the intact egg, but sudan black does readily. The rate of entry of the latter differs somewhat with the varieties of silkworm. Here the thickness of the exochorion is important in slowing down the rate of passage. The activity of the embryo seems also to concern with this. The diapausing eggs show a great resistance to the penetration of the dye, but in the developing eggs such as those under incubation in spring or activated artificially by the treatment with HCl during a few days after being laid it takes place more easily.<br>3. There is an asymmetrical permeability of acids in the isolated chorion. It is far resistant from without inwards than from within outwards.<br>4. The penetration of acids through the isolated chorion is enormously accelerated after its innerside has been wiped with chloroform. This does not happen with the outside wiping. There is also no increase in the penetration rate from within outwards by the chloroform treatment. It thus appears that the wax layer which is supposed to be deposited just beneath the endochorion offers the effective barrier to the inward penetration of the liquids, though it has no connection with that in the opposite direction.

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