806 THE NEUVES. 



Termination of the Nerves. — This point should be examined separately 

 in the ease of the motor and the sensitive nerves — that is, in the muscles and 

 the integumentary membranes. The distinction, however, is not quite so abso- 

 lute as this, for the muscles always receive some sensitive tubes with their motor 

 filaments. 



In entering the muscles the motor nerves divide their branches, still appearing 

 as double-contoured tubes. It was at one time believed that these fibres formed 

 loops (Valentin) in the interior of the muscle, and retm-ned to their starting- 

 point. This opinion has become obsolete since the ultimate termination of the 

 nerves has been studied by Rouget, Krause, Kiihne, KolUker, Engelmann, Ranvier, 

 and others. "What is known of this subject is as follows : The voluminous, 

 double-contoured nerve-tubes which, more or less, cross the direction of the 

 muscular fibres, soon divide and form pale tubes, with nuclei disseminated on 

 their course. These tubes contain an axis-cylinder and a medullary layer. They 

 pass on to a muscular fibre in the following manner : the nucleated sheath of 

 the nerve-tube spreads, and is confounded with the sarcolemma ; the medulla 

 suddenly stops when it has reached the motor end-plate, which is granular and 



Fig. 449. 



MUSCULAR FIBRES, WITH TERMINATION OP MOTOR NERVE (FROM THE GASTROCNEMIUS 

 OF THE RANA ESCULENTA). 



a, Terminal pencil of a dark-bordered nerve-fibre ; 6, intramuscular naked axis-cyliuder ; c, nucleus 

 of the neurilemma ; d, clavate extremities of the nerve ; e, spaces of the muscle-nuclei ; /, terminal 

 knob of nerve, with central fibres and vesicular dilatations of the nerve. 



has small nuclei. The axis-cylinder enters this little plate, and breaks up into 

 fibrillfe, which terminate in a manner unknown on coming into contact with the 

 contractile fibrillae. 



(When the ultimate nerve-fibre approaches the muscular fibre, the former 

 loses the white substance of Schwann, while the axis-cylinder pierces the sarco- 

 lemma and terminates in the tnotor end-plate. These plates vary much in form 

 and general appearance. Sometimes they seem to consist of very minute fibres, 

 formed by the splitting up of the axis-cylinder, anastomosing so as to form a 

 network, but usually they take the form of irregularly shaped granular masses 

 or discs, containing numerous vesicular nuclei.) 



The mode of termination of the sensitive nerves varies, according as they are 

 sensorial or general sensibility nerves. 



It appears to be demonstrated that the tubes of the sensorial nerves have at 

 their extremity an elongated cell, analogous to that from which they started. 

 An idea has been given of this arrangement in describing the olfactive portion of 



