14G 



NERVOUS TISSUE. 



sinuous, or somewhat tortuous in their course. They bear nuclei, some 

 of which, no doubt, may appertain to the prolongation of the primitive 

 sheath ; but others, generally fusiform and granular, are interposed, as 



Fig. 98. 



Fig. 98.— Small Branch op a Muscular Nerve of the Frog, near its Termina- 

 tion, SHOWING DIVISIONS OF THE FiBRES. MAGNIFIED 350 DIAMETERS (Kolliker). 



rt, into two ; h, into three. 



it were, in the course of the fibres, and are continuous with them at 

 either end ; nuclei, moreover, of a triangular or irregular shape, are 

 common at the bifurcations of the fibres. These pale fibres often join 

 into networks ; but their further disposition in different parts will be 

 treated of l^elow. In the meantime it must be explained that the 

 original dark-bordered fibres which thus undergo division and change, 

 or which may proceed singly to end in a different and special manner, 

 are commonly provided with a tolerably strong sheath with nuclei, 

 which, as it stands well apart from the dark borders of the fibre, is very 

 conspicuous. This is sometimes considered to be only the primitive 

 sheath of the fibre modified in character, but it seems more probable 

 that it is derived from the neurilemma or perineurium which incloses 

 the fine bundles or funiculi, and, as these part into smaller collections 

 and single fibres, undergoes a corresponding division, and finally sends 

 sheaths along single fibres. 



In further treating of the termination of nerves, it will be convenient 

 to consider the sensory and motor nerves separately. 



Termination of sensory nerves. — Of the sensoiy, or, at least, 

 non-muscular nerves, the following modes of final distribution have 

 been recognised. 



A. By networks, or terminal plexuses. These are formed by the 



