GENERAL ANATOMY. 49? 



The vesicular nervous substance is distinguished by its dark reddish-gray 

 color, and soft consistence. It is found in the brain, spinal cord, and various 

 ganglia, intermingled with the fibrous nervous substance, but is never found in the 

 nerves. It is composed, as its name implies, of vesicles or corpuscles, commonly 

 called nerve or ganglion corpuscles, containing nuclei and nucleoli ; the vesicles 

 being imbedded either in a finely granular substance, as in the brain, or in a 

 capsule of nucleated cells, as in the ganglia. Each vesicle consists of an exceed- 

 ingly delicate membranous wall, inclosing a finely granular material, part of 

 which is occasionally of a coarser kind, and of a reddish or yellowish-brown 

 color. The nucleus is vesicular, much smaller than the vesicle, and adherent to 

 some part of its interior. The nucleolus, which is inclosed within the nucleus, is 

 vesicular in form, of minute size, and peculiarly clear and brilliant. The nerve 

 corpuscles vary in shape and size; some are small, spherical, or ovoidal, with an 

 uninterrupted outline ; these forms being most numerous in the ganglia of the 

 sympathetic. Others, called caudate or stellate nerve corpuscles, are characterized 

 by their larger size, and from having one or more tail-like processes issuing from 

 them, which occasionally divide and subdivide into numerous branches. These 

 processes are very delicate, apparently tubular, and contain a similar granular 

 material to that found within the corpuscle. Some of the processes terminate 

 in fine transparent fibres, which become lost among the other elements of the 

 nervous tissue ; others may be traced until, after losing their granular appearance, 

 they become continuous with an ordinary nerve fibre. 



The Ganglia may be regarded as separate and independent nervous centres, of 

 smaller size and less complex structure than the brain, connected with each other, 

 with the cerebro-spinal axis, and with the nerves in various situations. They are 

 found on the posterior root of each of the spinal nerves ; on the posterior or 

 sensory root of the fifth cranial nerve; on the facial nerve; on the glosso- 

 pharyngeal and pneumogastric nerves ; in a connected series along each side of 

 the vertebral column, forming the trunk of the sympathetic ; on the branches of 

 that nerve in the head, neck, thorax, and abdomen ; or at the point of junction 

 of branches of that nerve with the cerebro-spinal nerves. On section, they are 

 seen to consist of a reddish-gray substance, traversed by numerous white nerve 

 fibres : they vary considerably in form and size, the largest being those found in 

 the cavity of the abdomen; the smallest, the microscopic ganglia, which exist 

 in considerable numbers upon the nerves distributed to the different viscera. 

 The ganglia are invested by a smooth and firm closely-adhering membranous 

 envelope, consisting of dense areolar tissue and continuous with the neurilemma 

 of the nerves. It sends numerous processes into the interior of the ganglia, 

 which support the bloodvessels supplying its substance. 



In structure, all ganglia are essentially similar, consisting of the same 

 structural elements as the other nervous centres, viz., a collection of vesicular 

 nervous matter, traversed by tubular and gelatinous nerve fibres. The vesicular 

 nervous matter consists of nerve cells or ganglion -globules,, most of which appear 

 free, and of a round or oval form, being more especially seated near the 

 surface of the ganglion ; others have caudate processes, and give origin to nerve 

 fibres. In the ganglia, the nerve cells are usually inclosed in a capsule of 

 granular corpuscles and fibres. The tubular nerve fibres run through the 

 ganglion, some being collected into bundles ; others, separating from each other, 

 take a circuitous course among the nerve cells before leaving the ganglia. 



The Nerves are round or flattened cords, communicating, on the one hand, with 

 the cerebro-spinal centre or the ganglia, and, by the other, distributed to the 

 various textures of the body, forming the medium of communication between 

 the two. 



The nerves are subdivided into two great classes, the cerebro-spinal, which 



proceed from the cerebro-spinal axis, and the sympathetic or ganglionic nerves, 



which proceed from the ganglia of the sympathetic ; the cerebro-spinal are the 



nerves of animal life, being distributed to the organs of the senses, the skin, and 



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