PHYSIOLOGICAL ANATOMY OF THE NERVOUS TISSUE. 



571 



itself has exactly the granular appearance of the substance of the axis-cylinder in the 

 vertebrata, and of that of the nerve-tubes in most of the invertebrata, especially after 

 being treated by diluted acids. But that which essentially characterizes the terminal 

 plates of the motor nerves is an agglomeration of nuclei observed at their site. With a 

 low magnifying power, even, we can distinguish the point where a nerve-tube touches 

 the primitive fasciculus to which it belongs, and ends abruptly at its surface, by a collec- 

 tion of from six to twelve or even sixteen nuclei which occupy the site of the terminal 

 plate. These nuclei are distinguished by their size as well as by their form, which is less 

 elongated than the nuclei of the muscular tissue (connective- tissue nuclei of the primitive 

 fasciculi). They present, however, the most complete analogy with the nuclei of the 

 nerve-sheath (connective-tissue nuclei of the nerves). They are, without any doubt, nothing 

 else than the nuclei which, scattered throughout the entire length of the sheath, are col- 

 lected in a mass at the point where the covering of the nerve-fibre is spread out and fuses 

 with the sarcolemma of the primitive fasciculus." 



There can be little if any doubt that the description just given represents the mode 

 of termination of the nerves in the voluntary muscles in man and in the mammalia. The 

 observations of Kolliker, who describes a plexus of pale fibres with nuclei instead of a 

 well-defined terminal plate, were made upon frogs, and are probably correct ; and Kolli- 

 ker admits the accuracy of the observations of Rouget as regards reptiles, birds, and the 

 mammalia. 



Although the sensibility of the muscles is slight as compared with that of the tegu- 

 mentary tissues, they undoubtedly possess nerve-fibres other than those exclusively 

 devoted to motion. In addition to the fibres just described, Kolliker and some others 

 have noted fibres with a different mode 

 of termination. These Kolliker believes 

 to be sensitive nerves, and their mode of 

 termination has not been so definitely de- 

 scribed as that of the fibres with terminal 

 motor plates. We refrain from giving a 

 very full description even of what has 

 been observed with regard to the termi- 

 nation of these fibres, for future and 

 more successful researches will probably 

 modify the views now held with regard 

 to this point. Kolliker states that the 

 fibres in question are very fine, dark-bor- 

 dered tubes, with a medullated sheath, 

 which, when studied in muscular tissue 

 rendered pale by acetic acid, may be seen 



FIG. 



176. Mode of termination of the motor nerves. 

 (Eouget.) 



A, primitive fasciculus of the thyro-hyoid muscle of the human 



subject, and its nerve-tube : 1,1, primitive muscular fas- 

 ciculus; 2, nerve-tube; 3, medullary substance of the 

 tube, which is seen extending to the terminal plate, where 

 it disappears ; 4, terminal plate situated beneath the sar- 

 colemma, that is to say, between it and the elementary 

 fibrillse; 5, 5, sarcolemma. 



B, primitive fasciculus of the intercostal muscle of the lizard, 



in which a nerve-tube terminates : 1, 1, sheath of the 

 nerve-tube , 2, nucleus of the sheath ; 3, 8, sarcolemma 

 becoming continuous with the sheath : 4, medullary sub- 

 stance of the nerve-tube ceasing abruptly at the site of the 

 terminal plate ; 5, 5, terminal plate ; 6, 6, nuclei of the 

 plate ; 7, 7, granular substance which forms the principal 

 element of the terminal plate, and which is continuous 

 with the axis-cylinder ; 8, 8, undulations of the sarcolem- 

 ma reproducing those of the fibrillae; 9, 9, nuclei of the 

 sarcolemma. 



to give off exceedingly fine, non-medul- 

 lated fibres, which terminate in fibres of 

 the same appearance, but provided with 

 nuclei. It does not appear to be certain 

 how these fibres end. Kolliker is not 

 satisfied that the free extremities, as 

 they appear to be, are the actual termi- 

 nations; but he asserts that in some rare 

 instances they communicate with each 

 other. For the present this point must 

 be considered as unsettled. 



Mode of Termination of the Nerves in the Involuntary Muscular Tissue. The nerves 

 have not been followed out so satisfactorily in the involuntary as in the striated mus- 

 cular system ; and, as most if not all of the fibres are derived from the sympathetic 



