NERVOUS TISSUE. 189 
off a branch, more or fewer of these tubes divide, sending 
off a prolongation into each branch. 
When quite fresh, the contents of the tubes are per- 
fectly pellucid, and without the least indication of struc- 
ture; and, from the xanner in which the contents 
Fic. 55.— Astacus fluviatilis —Three nerve fibres, with the zonnective 
tissue in which they are imbedded (magnified about 250 diameters) ; 
n, nuclei. 
exude from the cut ends of the tubes, it is evident that 
they consist of a fluid of gelatinous consistency. As the 
fibre dies, and under the influence of water and of many 
chemical re-agents, the contents break up into globules 
or become turbid and finely granular. 
Where motor nerve fibres terminate in the muscles to 
which they are distributed, the sheath of each fibre 
becomes continuous with the sarcolemma of the muscle, 
and the subjacent protoplasm is commonly raised into a 
small prominence which contains several nuclei (fig. 52, F). 
These are called the terminal or motor plates. 
