294 THE HUMAN BODY. 



lie in two rows (s, Fig. 1, and sy, Fig. 2), one on each side 

 of the bodies of the vertebrae. Each ganglion is united by a 

 nerve-trunk with the one in front of it and the one behind it, 

 and so two chains are formed reaching from the base of the 

 skull to the coccyx. In the trunk region these chains lie in the 

 ventral cavity, their relative position in which is indicated 

 by the dots sy in the diagrammatic transverse section repre- 

 sented on p. 9 in Fig. 2. 



Each sympathetic ganglion is united by branches to 

 neighboring spinal nerves, and near the skull to various 

 cranial nerves also; from the ganglia and their uniting cords 

 arise numerous trunks, which in the thorax and abdomen 

 form networks, from which nerves are given off to the or- 

 gans situated in those cavities. Many sympathetic nerves 

 finally end in the walls of the blood-vessels of various or- 

 gans. To the naked eye they are commonly grayer in color 

 than the cerebro-spinal nerves. 



By means of the junctions between the cranial and spinal 

 nerves and the sympathetic system the brain is enabled to 

 control the parts supplied by the sympathetic system. 



The Three Kinds of Nerve Tissue. The microscope 

 shows that the nervous organs contain tissues peculiar to 

 themselves, known as nerve-fibres and nerve-cells. The 



How are the ganglia of the sympathetic system arranged? 



How is each united to others? How far through the body do 

 the chains of sympathetic ganglia extend? Where are the sym- 

 pathetic chains situated in the trunk of the body? 



How are the sympathetic ganglia united with spinal and cranial 

 nerves? What arise from the ganglia? What do they form in the 

 trunk region of the body? Where do many sympathetic nerve- 

 fibres end? How do sympathetic nerves differ to the unaided eye 

 from spinal or cerebral nerves? How is the brain enabled to control 

 the parts supplied by the sympathetic system ? 



How many kinds of nerve-tissue are there? What are the pecul- 

 iar nerve-tissues called ? 



