570 NERVOUS SYSTEM. 



Mode of Termination of the Nerves in the Voluntary Muscles. For a long time, the 

 mode of termination of the nerve-fibres in the muscles was a question of great uncer- 

 tainty ; but, within the last few years, thanks to the elaborate researches of French and 

 German anatomists, the peripheral extremities of the nerves have been so accurately 

 described and figured, that the great question of the mode of connection between the 

 anatomical element conducting the stimulus to the muscles and the contractile elements 

 of the muscles themselves may be considered as definitively settled. In 1840, Doyre gave 

 an account of the peripheral termination of the motor nerves, probably as accurate as 

 was possible with his imperfect means of investigation ; but this observation, though 

 confirmed a few years later by Quatrefages, seems to have been lost sight of by most 

 physiological writers. Without underestimating the value of other researches, we may 

 state that those of Rouget represent, perhaps, the present condition of the question as 

 well as any. The differences, however, between the most reliable observations of recent 

 writers are nearly all unimportant ; and, while future investigations may enable us to go 

 farther in following out some of the elements of the nerve-fibres, they will, in all probabil- 

 ity, simply extend our knowledge, without invalidating the information already acquired. 



The observations of Rouget were published in 1862 and were made upon lizards, 

 frogs, Guinea-pigs, rats, and other animals, and have been confirmed in the human subject. 

 The tissues were taken either from the living animal or from an animal just killed, and 

 they were examined, in some instances, without the addition of reagents ; hut the most 

 satisfactory results were obtained by macerating the muscles for from six to twenty-four 

 hours in a liquid containing ^-^ of hydrochloric acid, and adding to the preparation on 

 the glass slide a drop of a solution of sugar in water. In preparations made in this way, 

 it is easy to trace the course of the nerves to their termination. The following is the 

 description given by Rouget : 



" The nervous trunks and the branches of distribution generally cross the course of 

 the muscular fibres. As regards the terminal ramifications, sometimes they meet the 

 muscular fibres at nearly a right angle, and sometimes they are placed nearly parallel to 

 the axis of the primitive fasciculi. Branches of distribution are detached sometimes 

 from branches containing two or three fibres, and sometimes from isolated fibres. After 

 a very short course these tubes divide, and may present as many as seven or eight suc- 

 cessive divisions. Most commonly, the termination takes place either by divisions of the 

 second or third order, or the same tube gives off, successively, divisions which pass to the 

 adjacent primitive fasciculi and terminate here without new divisions and after a very 

 short course. They have a less diameter than the primitive nerve-tubes, but they pre- 

 serve even to the terminal extremity their double contour, and there can be demonstrated, 

 very easily, a sheath provided with nuclei, a medullary layer, and the axis-cylinder. 

 Never do we observe at the termination of the motor nerves the pale and non-medullated 

 fibres described by Ktihne and Kolliker. At the point where the tube terminates, we 

 remark constantly a special arrangement which has no analogy with that which has been 

 described in the batrachia by these two observers, and which Ktihne believed could be 

 extended to the higher vertebrata, to. the mammalia, and to the human subject. The 

 nerve-tube, with a double contour, preserving still a diameter of from ^Vo to T ^ of an 

 inch at the point where it touches the primitive fasciculus to become arrested at its sur- 

 face, terminates by an expansion of the central nerve-substance, the axis- cylinder, which 

 is in immediate contact with the contractile fibres (fibrillse) of the primitive fasciculus. 

 The layer of medullary substance ceases abruptly at this point, the sheath of the tube is 

 spread out and blended with the sarcolemma; but in immediate continuity with the axis- 

 cylinder, a layer, a plate of granular substance, from -^Vs- to oVo of an incn in thick- 

 ness, is spread out beneath the sarcolemma, on the surface of the fibrilla?, in a space 

 generally oval and about T ^ 7 7 of an inch wide in its short diameter, and -5-^ of an inch 

 in its long diameter. This granular substance masks more or less completely, in the 

 space which corresponds to it, the transverse stri.88 of the muscular fasciculus. The disk 



