ARRANGEMENT OF NERVES. 217 



nature and function are essentially those of nervous centres. 

 Some of them belong to the cerebro-spinal system of nerves 

 e. f/.j most of the ganglia connected with the cerebral nerves 

 and those on the posterior roots of the spinal nerves ; others 

 pertain to the sympathetic system, as the lateral and anterior 

 spinal and the visceral ganglia. 



Typical ganglia are enveloped in a fibrous capsule continu- 

 ous with the epineurium of the tributary nerves. The nerve- 

 ceils in the ganglia are aggregated in elongated or rounded 

 clusters, separated by bundles of (rnedullated or non-medul- 

 lated) nerve-fibres. Each nerve-cell is surrounded by a 

 membranous nucleated capsule, composed of connective-tissue 

 cells, continuous with the neurilemma of the issuing nerve- 

 fibre. 



The ganglia of the posterior roots of the spinal nerves con- 

 sist of medullated fibres and large globular encapsulated 

 nerve-cells, nucleated and nucleolated. In man these nerve- 

 cells when mature possess a single process which at a short 

 distance from the cell divides like a T into two branches 

 going in contrary directions ; these cells are practically bipolar, 

 as they actually are morphologically in some animals and 

 the human embryo. 



The sympathetic ganglia similarly consist of nerve-fibres 

 (non-medullated and medullated) and nerve-cells. The latter 

 are encapsulated, multipolar, often pigmented, occasionally in 

 man (regularly in some animals) possessing two nuclei. Many 

 of the sympathetic ganglia are very minute, imbedded in the 

 substance of the viscera, as the heart and the intestines. 



The Nerves. 



The nerves, or nerve-trunks, consist of bundles of nerve-fibres 

 bound together by sustentacular connective tissue. 



The cerebro-spinal nerves consist mainly of medullated 

 fibres ; the sympathetic nerves chiefly of non-medullated fibres. 



The arrangement of nerves (especially the cerebro-spinal) 

 corresponds to that of voluntary muscle. The individual 

 fibres are grouped in bundles or " funiculi " ; and these again 

 into the entire nerve-trunks (except in small nerves consisting 

 of single funiculi). The entire nerve is enveloped in a con- 



