NEUROLOGY 279 



Neurones are devoted to the maintenance of functions. Repro- 

 ductive neurones are so arranged as to receive afferent nerve impulses 

 from other tissues; emissive neurones give off efferent nerve impulses. 

 The former are sensory neurones; the latter are motor neurones 

 if connected with muscles, and excito-glandular if connected with 

 gland cells. The basis, then, of the nerve system is a series of neu- 

 rones, with projecting and association processes, coordinated for 

 the purpose of performing specific actions manifested either by 

 motion, by trophic changes, or by the apperception of stimuli of 

 a chemic, mechanic (tactile and auditory), thermal, or photic nature. 



The whole of the nerve structure is composed of the nerve tissue 

 and supporting connective tissue. The neurones constitute the 

 nerve tissue, while the supportive tissue is composed of neuroglia 

 and of white fibrous tissue derived either from the investing mem- 

 brane or from the sheaths of its numerous vascular channels. 



The neurones, or nerve cells, exhibit marked variations as to ex- 

 ternal characters, dimensions, and form. The neurone presents a 

 swollen cell mass and a nucleus; it is known as the ganglion cell. 

 From this cell body are given off a number of processes of two dis- 

 tinct kinds: first, protoplasmic processes, which are commonly 

 branched, called dendrites; second, a single, thinner, and paler proc- 

 ess; the axis cylinder process. 



juncture between the muscle and tendon. Note the many nuclei in both muscle 

 and tendon. This is voluntary or striated muscle which make up the dermal, 

 dermo-osseous and skeletal muscles. 



4. A longitudinal section of heart muscle, a, Connective-tissue cell, b, 

 Nucleus of a muscle cell, c, Cement line between the muscle discs, d, The 

 cell or segment. 



5. A bipolar ganglionic nerve cell, a, The nucleus. &, The nucleolus. c, The 

 fibrillar structure, d, The medullary sheath. 



6. A diagram showing the scheme of the peripheral nerve trunk, a. The 

 neuraxis of the peripheral sensory neurone, b, The spinal ganglion of the 

 superior or sensory root, c, The dendrite or peripheral nerve fiber of the sensory 

 nerve, d, The nerve trunk. /, The sympathetic nerve ganglion connected with 

 the spinal cord through the white and the gray ramus communicans. e. The 

 neuraxis of the sympathetic neurone, g, Neuraxis or trunk of the motor neurone 

 or nerve cell, h, The anterior horn of the gray matter of the spinal cord. 



7. A diagram of a peripheral sensory neurone, a, The neuraxis which ends 

 in the spinal cord or brain, b, The T-shaped division of Ranvier. c, The den- 

 drite or sensory nerve fiber in the nerve trunk, d, The nucleus and nucleolus 

 of the cell e., f. the axis cylinder process of the cell, g, The telodendrions or 

 terminal branches of the dendrite or axis cylinder. 



8. A schematic diagram of the sensory motor reflex, a, The telodendria. 

 6, The dendrite. c, Nerve cell of the motor neurone, d, The motor neurone. 

 /, The muscle fiber, g, The neuraxis of both sensory and motor neurones, the 

 upper being the sensory, h, the nerve cell in the sensory ganglion. *, The 

 sensory neurone or axis cylinder (nerve fiber), j. The skin with peripheral 

 telodendrion of sensory neurone. 



