Blastomere
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
This article from the 1928–1936 Soviet Great Medical Encyclopedia defines blastomeres as the cleavage cells formed during the division of the fertilized egg in multicellular animals. It describes how their size and distribution vary depending on whether the cleavage is uniform, as in sea urchins, or unequal, as in ganoids and amphibians.
Encyclopedia entry (1928–1936)
BLASTOMA, see Tumors. BLASTOMERES (from the Greek blastos, germ, and meros, part), cleavage spheres, the cells into which the fertilized and dividing egg of all multicellular animals breaks down. With equal cleavage (for example, in sea urchins), all blastomeres are equal in size; with unequal cleavage (ganoids, amphibians), one distinguishes micromeres—blastomeres of a smaller size located at the upper, animal pole—and macromeres of the lower, vegetative pole, which are larger blastomeres due to a higher yolk content.
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“Blastomere.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.pages.dev/article/blastomere/