The development of the human body; a manual of human embryology . terior root ganglion en masse, migrate from it singly orin groups, and are therefore less readily distinguishablefrom the surrounding mesodermal tissues. To understand the development of the sympatheticsystem it must be remembered that it consists typicallyof three sets of ganglia. One of these is constituted bythe ganglia of the ganglionated cord (Fig. 233, GC), thesecond is represented by the ganglia of the prevertebralplexuses (PVG), such as the cardiac, solar, hypogastric,amd pelvic, while the third or peripheral set (PG) is
The development of the human body; a manual of human embryology . terior root ganglion en masse, migrate from it singly orin groups, and are therefore less readily distinguishablefrom the surrounding mesodermal tissues. To understand the development of the sympatheticsystem it must be remembered that it consists typicallyof three sets of ganglia. One of these is constituted bythe ganglia of the ganglionated cord (Fig. 233, GC), thesecond is represented by the ganglia of the prevertebralplexuses (PVG), such as the cardiac, solar, hypogastric,amd pelvic, while the third or peripheral set (PG) is formedby the cells which occur throughout the tissues of proba-bly most of the visceral organs, either in small groups orscattered through plexuses such as the Auerbach andMeissner plexuses of the intestine. Each cell in thesevarious ganglia stands in direct contact with the axis-cylinder of a cell situated in the central nervous system,probably in the lateral horn of the spinal cord or the cor-responding region of the brain, so that each cell forms the 37 I 4. :-,--^f- ft ^ • ^ Fig. 232.—Transverse Section through an Embryo Shark (Scyllium) OF 15 MM., SHOWING THE ORIGIN OF A SYMPATHETIC GANGLION. Ch, Notochord; E, ectoderm; G, posterior root ganglion; Gs, sympathetic ganglion; M, spinal cord.—(Onodi.) 442 THE SYMPATHETIC SYSTEM. 443 terminal link of a chain whose first link is a neuronebelonging to the central system (Huber). Throughoutthe thoracic and upper lumbar regions of the body thecentral system neurones form distinct cords known as thewhite rami communicantes (Fig. 233, WR), which passfrom the spinal nerves to the adjacent ganglia of the gan-glionated cord, some of them terminating around the cellsof these ganglia, others passing on to the cells of the pre-vertebral ganglia, and others to those of the peripheral
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
