File:The Farm-poultry (1901) (14596885780).jpg

Identifier: farmpoultry129unse (find matches)
Title: The Farm-poultry
Year: 1901 (1900s)
Authors:
Subjects: Poultry Northeastern States Periodicals Poultry Industry Northeastern States Periodicals
Publisher: Boston, Mass. : I.S. Johnson and Co.
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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e subject of biology. It is important that these facts should beconsidered at the outset; for such is the arro-gance of science, such her evasion of questionswhii-h she is unable to answer, and such herassumption of authority that the reader is iu in the development of the brain, spinal cord,nerves, ej e~. epidermis, scales, nail-, feathers,ami the mucous membranes of the mouth,throat and nose. The inner layer, or hypo-blast, gives rise to the epithelium lining theintestines. From the outer layer of the myo-blast are developed the muscles of the trunk,and the bony framework of the body. Fromthe inner stratum the various internal organs,the blood and the blood vessels. While the development of these membranesis in progress there appears at the originalseat of the genu a tiny transparent furrowcalled the primitive trace. Shortly after itsformation ridges begin growing along itsmargins. These, increasing in height andbending inward, unite to form a closed tube,the neural canal. Fig. 85s1
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Diagrams to show the development of the three layers of the blastodermic (vesicle or) membrane in transverse sections: — A, portion of the ovum with the zona pellucida and the germinal area, B, C, D, E, F, G, different stages of development; o, umbilical vesicle: a, amnion: f, intestine; p, peritoneal cavity, bounded by the splanchno-pleural and somato-pleural layers of mesoblast; 1 vitelline membrane; 2, external blastodermic layer (epiblast): 3, middle layer (mesoblast): 4, internal layer (hypoblast): 5, medullary lamina and groove; 5’, medullary canal: 6, epidermic lamina: 7. lateral flexures of the amnion: 7, the same almost in contact: 8, internal epithelial layer of the amnion; 9 epidermis of the embryo; 10, chorda dorsalis (notochord); 11, vertebral laminae: 12, protovertebrie proper: 13, muscular laminae: 14, lateral laminae: 15, fibro-intestinal laminae; 16, cutaneous laminae; 17, internal fibrous layer of the umbilical vesicle; 18, muscular laminae extending to meet the cuta- neous; 19, external layer of the cutaneous laminae; 20, internal layer of the same; 21, mesentery; 22, fibrous layer of the intestine.

1. The dotted lines indicate the parts belonging to the internal blastodermic layer; the plain lines, those belonging to the middle; the interrupted lines, those belonging to the external, The embryo has been repre- sented in this and the following diagram, lying on its back; the natural position is generally assumed to be the reverse.
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