132 THE NERVOUS SYSTEM. 
PERIPHERAL NERVES 
‘What changes occur in peripheral nerves after division and separa- 
tion from their trophic centres ? 
The medullary sheath breaks up into various-shaped droplets which 
become decomposed with the formation of fat. The axis cylinder is 
- often destroyed. The nerve sheath with its nuclei does not usually 
degenerate. Sometimes after a variable period the nerve fibres become 
regenerated. 
Name the different inflammations of the peripheral nerves. 
Acute exudative neuritis. 
Chronic interstitial neuritis. 
Multiple neuritis. 
What are the pathological changes in acute exudative neuritis ? 
The inflamed nerve is red and swollen and infiltrated with serum and 
pus. The process may undergo resolution or terminate in gangrene 
and destruction of the nerve. 
What are the changes in chronic interstitial neuritis ? 
There is an increased growth of connective tissue in the nerve 
sheaths and intrafascicular bands with a consequent atrophy of the 
nerve fibres. 
What are the causes of and changes in multiple neuritis ? 
On account of exposure to wet or cold, alcoholism, poisoning by lead 
or arsenic, a degeneration of the nerve fibres in different parts of the 
body may occur. This degeneration may be accompanied or followed 
by a proliferation of the neurilemma cells, In some forms of multiple 
neuritis there is an exudative inflammation, and new cells are found in or 
between the nerve fibres. Regeneration may take place after these 
changes. 
What tumors have been found in peripheral nerves? 
True neuromata, false neuromata, consisting of fibrous or myxo- 
matous tissue; myxo sarcomata and primary sarcomata. Carcinomata 
and sarcomata may occur as secondary growths. 
