. Text book of zoology. Zoology. Cells and Tissues. 13 ramify over it or its processes (Pig. 15, 3). There is yet a third kind of ganglion cell connected with neither epithelium nor muscle, but only with other ganglion cells (Fig. 15, l). It maybe noticed here that many gland cells, like muscle cells, only become active when they receive a stimulus from a ganglion cell; in glands, therefore, terminal branches of ganghon processes are present in great MWJJ MM m Fig. 15. Various ganglion cells, etc. 1 Ganglion cell, with dendritic, but without the longer prouesses. 2 Motor ganglion cel
. Text book of zoology. Zoology. Cells and Tissues. 13 ramify over it or its processes (Pig. 15, 3). There is yet a third kind of ganglion cell connected with neither epithelium nor muscle, but only with other ganglion cells (Fig. 15, l). It maybe noticed here that many gland cells, like muscle cells, only become active when they receive a stimulus from a ganglion cell; in glands, therefore, terminal branches of ganghon processes are present in great MWJJ MM m Fig. 15. Various ganglion cells, etc. 1 Ganglion cell, with dendritic, but without the longer prouesses. 2 Motor ganglion cell connected to a muscle cell m by a nerve fibre n. 3 Two ganglion cells connected with one another. 4 Sensory ganglion cell, with its nerve fibre branching in the epithelium e. 5 Sensory ganglion cell g, with two long processes; b the terminal tuft of the process. 6 Sense cells s; b the terminal tuft of an efferent nerve fibre ; a ganglion cell below.—Orig. The long processes of ganglion cells are called nerve fibres, and according to their connection with muscle or with sense cells, they are called motor or sensory: the short processes are termed dendrites. Sometimes nerve fibres originate not in ganglion, but in sensory, cells (Fig. 15, 6) : the epithelial cells are, in this case, usually tall, narrow cells, with a tuft or fringe of cilia at the free end; they pass, on the inner side, into long delicate processes, which are intimately connected with ganglion cells, for the end breaks up into a fine anastomosis, which is closely apposed to a ganglion cell or its processes. Such epithelial cells are called sensory cells, and the prolongations, sensory nerve fibres. The nerve fibres are frequently enveloped in sheaths of speoiaUy developed connective tissue. Most of those in Vertebrates have a double sheath, a strongly refringent fatty medulla within, and an outer neurilemma or sheath of Schwann. Some vertebrate nei-ve fibres are covered vsdth a neurilemma only. II. Organs. Al
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
