Template talk:Ref-Bryce1924

Early Development Of The Human Embryo

NOVEMBER 15, I924 NATURE p729

Prof, T. H. Bryce’s “ Observations” on this subject have just been published as a separate memoir in the Transactions of the Royal Society of Edinburgh (vol. 53, Part 3, 1924). They should be studied in conjunction with Prof. Teacher’s paper on the implantation of the ovum, which was recently noticed in NATURE (Sept. 6, p. 367). Indeed the two memoirs deal largely with the same material, but from different points of view, and so supplement one another. Prof. Bryce, however, besides describing the two Teacher-Bryce Ova, includes an account of an entirely new early embryo obtained by Dr. Donald M‘Intyre from a uterus removed surgically by sub total hysterectomy. The memoircontains a number of important observations, some of which are confirmatory of former discoveries and some of which are new. ln dealing with the primitive extra-embryonic inesoderm, it is shown that this is primarily an angioblastic tissue. All round the young chorion the formation of vascular channels has begun in it (in the second Teacher-Bryce ovum) before there are any vessels in the yolk-sac and apart from the formation of blood corpuscles. The embryo is afterwards linked up with this system of vascular channels through vessels developed in the allantoic stalk. The author also describes the primary connexions of the yolk-sac and chorion, and points out that the observations support the view that the small size of the yolk—sac in the primates is a secondary condition, its recession being very precocious, but. agreeing essentially with what occurs at a later stage in many of the lower mammals. The yolk-sac duct, which is described, is regarded as a vestigial structure reminiscent of a phylogenetic phase when the organ was of larger size. The memoir contains also new and interesting facts relating to the amnion and its duct, the primitive streak and the archenteric canal. It is illustrated by nine plates containing nearly fifty well-executed figures.