FIBRES  may be medullated or non-medullated, but, whichever they are, they consist of the See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long See also:

• PROCESS

process or axon of a See also:

• NERVE (Lat. nervus, Gr. vevpov, a bowstring)

nerve See also:

• CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell; in a non-medullated nerve this process is either naked or enclosed in a delicate membrane called the See also:

• PRIMITIVE

primitive sheath or neurilemma, but in a medullated nerve the process or See also:

• AXIS (Lat. for " axle ")

axis See also:

• CYLINDER (Gr. KvAwSpos, from KvXivaety, to roll)

cylinder is encased by a See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

white fatty substance called myelin, and so the See also:

• TERM

term " myelinated " is often used instead of " medullated " for these nerves (see fig . 1) . Axis Outside this white sheath the neurilemma is cylinder See also:

• PRESENT

present in most nerves, but is lost when they are massed to See also:

• FORM (Lat. forma)

form the white See also:

• MATTER

matter of the central See also:

• NERVOUS

nervous See also:

• SYSTEM

system and in the optic nerve . Myelin At See also:

• REGULAR

regular intervals the myelin is interrupted by some substance which stains deeply with See also:

• SILVER

silver nitrate, and these breaks are known as nodes of Ranvier . They do not, however, affect the axis cylinder . In a large nerve, such as the median, the nerve fibres are collected into small Primitive bundles called funiculi, enclosed in a connective sheath See also:

• TISSUE (Fr. tissu, tissue, participle of tisser, Lat. texere, to weave)

tissue sheath, the perineurium, and separated from it by a See also:

• LYMPH

lymph space . From this sheath delicate processes penetrate among the fibres, and these are known as the endoneurium . The funiculi are collected into bundles called fascicuti, and the whole nerve consists of a variable number of fasciculi surrounded by a dense fibrous sheath, the epineurium . The various bundles do not remain distinct, but break up and re-arrange themselves, so that following them up with the scalpel is a difficult and tedious See also:

• WORK

work . The nerve fibres, however, never join one another and are often several feet in length .