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adult allantois amnion amniota amphibia anlage aorta aortic appears arch archenteron arise arteries auricle becomes blastoderm blastopore blood-vessels bone brain branches branchial canal cartilage cavity ccelom cells chick chorion concrescence connective tissue cord decidua dermal differentiation distinct dorsal side ectoderm embryo enamel enamel organ enlargement epidermis epithelial epithelium epitrichium fibres fissure fold follicle fore-brain ganglia ganglion genital gill-clefts glands groove grows growth hair heart homologous human embryo inner Kolliker later layer limbs longitudinal lower mammals median medulla medullary membrane mesenchyma mesoderm mesothelium Mihalkovics month mouth muscle myotome nerve notochord nuclei observations olfactory optic organ ossification outer ovum papilla placenta plate portion posterior primitive streak probably pronucleus protoplasm region ridge segments separate septum sinus somatopleure spermatozoon spinal stage surface thickening tion transverse tube tubules umbilical upper urogenital uterus veins ventral ventricle vertebrates vesicle vessels villi wall Wolffian body Wolffian duct yolk yolk-sac zone
Page 220 - ... by a very thin layer of protoplasm, which is very easily overlooked, especially if the preparation is not suitably stained; this explains, I think, the statement made by Balfour (Works, Vol. i) and others that the blood corpuscles consist only of nuclei. By following the development along further we find that the protoplasm enlarges for several days, and that during the same time there is a progressive diminution in size of the nucleus, which, however, is completed before the layer of protoplasm...
Page 85 - It is almost universally admitted that cells, or the units of the body, propagate themselves by self-division or proliferation, retaining the same nature and ultimately becoming converted into the various tissues and substances of the body. But besides this means of increase, I assume that cells before their conversion into completely passive, or
Page 85 - They are supposed to be transmitted from the parents to the offspring, and are generally developed in the generation which immediately succeeds, but are often transmitted in a dormant state during many generations and are then developed. Their development is supposed to depend on their union with other partially developed cells or gemmules which precede them in the regular course of growth.
Page 85 - I assume that cells, before their conversion into completely passive or "formmaterial," throw off minute granules or atoms, which circulate freely throughout the system, and when supplied with proper nutriment multiply by self-division, subsequently becoming developed into cells, like those from which they were derived...
Page 21 - Eiitwickelungsgeschichle (Third edition, pp. 216-217, fig. 147). Leopold holds that the epithelioid layer is the reflexa, but what has just been said suffices, I think, to show that this view is untenable. That the membrana decidua reflexa should degenerate and disappear no longer seems strange since recent investigations have shown that in many placental mammals there occurs an extensive pseudo-pathological destruction of the mucosa uteri during gestation. These changes, which are best known in...
Page 85 - It is universally admitted that the cells or units of the body increase by self-division or proliferation, retaining the same nature, and that they ultimately become converted into the various tissues and substances of the body. But besides this means of increase I assume that the units throw off minute granules which are dispersed throughout the whole system ; that these, when supplied with proper nutriment, multiply by self-division, and are ultimately developed into units like those from which...
Page 20 - ... persistence of the reflexa involve the further and very improbable assumption that the degenerated tissue is removed and replaced by fully organized cellular decidual tissue. It Is obviously more in accordance with our knowledge of degenerative changes to assume that the hyaline metamorphosis is necrotic and is succeeded by the disintegration and removal of the tissue. This accounts in a satisfactory manner for the absence of the decidua reflexa during the sixth and seventh month. The relations...
Page 19 - ... being a thin membrane, and the thinnest point being opposite the placenta. The examination of sections shows that the entire reflexa is undergoing degeneration , which is found to be the more advanced the more remote the part examined is from the placenta. The chorion laeve lies very near the reflexa, being separated only by chorionic villi, which are very much altered by degeneration, their ectoderm having become a hyaline tissue, which stains darkly and their mesoderm showing clearly the partial...
Page 223 - Tbe above review shows that the vertebrate blood corpuscles are of three kinds: (1) red cells; (2) white cells; (3) plastids. The red and white cells occur in all (?) vertebrates; the plastids are confined to the mammals. The red cells present three chief modifications; whether the primitive form occurs in any living adult vertebrate I do not know ; the second form is persistent in the Ichthyopsida, the third form in the Sauropsida. According to this we must distinguish : A. — One-celled blood,...
Page 220 - AccordIng to the above description we can distinguish three principal stages : — 1°, young cells with very little protoplasm; 2°, old cells with much protoplasm and granular nucleus ; 3°, modified cells with shrunken nucleus which colors darkly and uniformly.