. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 44 Biology of the Vertebrates and semi-transparent pelagic animals, such as medusae and ctenophores, in which the jelly-like bulk of the body is composed of secreted inter-cellu- lar material throughout which are scattered a few cells, frequently joined together in a very open meshwork by delicate cytoplasmic bridges. This type of tissue does not commonly appear in the bodies of adult vertebrates, al- though during embryonic development the so-called mesen
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 44 Biology of the Vertebrates and semi-transparent pelagic animals, such as medusae and ctenophores, in which the jelly-like bulk of the body is composed of secreted inter-cellu- lar material throughout which are scattered a few cells, frequently joined together in a very open meshwork by delicate cytoplasmic bridges. This type of tissue does not commonly appear in the bodies of adult vertebrates, al- though during embryonic development the so-called mesenchyme passes through a gelatinous tissue ~~~S"~ Nerve Cord ^» Connective Tissue Z-m Elastica Externa (Primary Sheath) ^Xv^iilâFibrous (Secondary) Sheath '---^âPeripheral Notochordal Cells Vacuolated Notochordal Cells *â Dorsal Aorta Fig. 98. Cross section through the notochord and its sheaths, from a young dogfish. In notochordal tissue, on the contrary, there is a great reduction of in- tercellular material, so that the thin-walled cells lie closely pressed together (Figs. 98 and 211). Whatever rigidity is attained by this tissue is due largely to the fact that the cells are so tightly packed within a tough sheath that a certain turgor results like that when sausage meat is crowded into a casing. Reticular connective tissues (Fig. 99) form the meshlike supports that characterize many of the softer organs, like the liver, spleen, and lymph nodes, which are ordinarily thought of as being without internal skeletal devices of anv Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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