GANGLIA. 



75 



Nerve-fibres, cut transversely 



Nerve-cell 



cells in mammals alwa) r s multipolar are surrounded by nucleated capsules 

 continuous with the neurilemma of the nerve-fibres. Many of the ganglion 

 cells give off sympathetic efferent axones, which, a's nonmedullated fibres, 

 join the splanchnic trunks and end 

 in the involuntary muscle of the various 

 internal. organs. Other neurones send 

 axones, by way of the gray rami com- 

 municantes, toward the periphery of 

 the body to be distributed, generally by 

 the paths followed by the cerebrospinal 

 nerves, to the outlying masses of invol- 

 untary muscle within the walls of the 

 blood-vessels, the sweat glands and the 

 skin. Among the cells of the sympa- 

 thetic ganglia often are mingled den- 

 drites, that are traversing the splanchnic 

 paths as afferent fibres, conveying sen- 

 sory impulses from the viscera, to reach 

 the ganglia on the posterior roots and, 

 eventually, the reception nuclei of the 

 spinal cord. Although the axones of 

 the sympathetic neurones for the most part are devoid of medullary sheath, 

 and appear as pale fibres, this condition often applies only to part of their 

 course. The spinal efferents, which join the sympathetic by way of the 

 white rami communicantes, are medullated fibres. Eventually, they too 



Supporting tissue 



Nonmedullated nerve- 

 fibres 



Ganglion cells 



Capsule 



Nerve-fibres 



FIG. ioi. Section of spinal ganglion, showing 

 urve-cells surrounded by nucleated capsules. 

 X3- 



FIG. 102. Portion of section of sympathetic (semilunar) ganglion from child. X 250. 



lose the myelin-sheath and, after a variable course as nonmedullated fibres, 

 end in arborizations composed of naked axis-cylinders that surround the 

 sympathetic ganglion cells. 



Under the paraganglia are included clumps or cord-like collections of 

 cells, which are derived from the formative areas of the sympathetic ganglia 

 and share with cells scattered throughout the sympathetic nerves and ganglia 



