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 tbe manner in which the contents 



Fig. 55. — Astacus fliiviatilis. — Three nerve fibres, with the connective 

 tissue in which they are imbedded (magnified about 250 diameters) ; 

 m, 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. 



