THE MODE OF TERMINATION OF MOTOR NERVES. 203 



investing membranes in the Tardigrada(or bear animalcules), and 

 the nervous and muscular tissues thus come into direct contact. 



The observation of Doyere long remained misunderstood, and 

 passed into oblivion in consequence of the general acceptance 

 of the view of Ernst Briicke and Joh. Miiller, to the effect 

 that the primitive nerve fibres undergo division between the 

 muscular fibres. It was, indeed, completely forgotten when 

 K. Wagner recognised with much discrimination the value of 

 that mode of nerve termination which Savi first discovered in 

 the electrical organs of the Torpedo, and applied it as a fact of 

 general significance to all peripherically distributed nerves. It 

 then first became intelligible how so small a number of nerve 

 fibres as those which are ordinarily contained in a motor nerve can 

 influence such a much larger number of muscular fibres. In a care- 

 fully written essay, Reichert showed that the pectoral cutaneous 

 muscle of the Frog, which is composed of about 160 muscular 

 fibres, receives only about six or seven primitive nerve fibres ; 

 but the proportion was no longer unintelligible when far more, in 

 fact nearly 300, terminal fibres, proceeding from the division of 

 the latter, could be proved to be present. Of these investiga- 

 tions, however, few or none were directed to the solution of the 

 question respecting the proper termination of *the nerves, but 

 rather to their mode of division between the muscular fasci- 

 culi. The latter point lies beyond the limits of the present 

 paper, and we shall therefore content ourselves with the descrip- 

 tion of what is of most importance in regard to it. 



When thin transparent muscles or thin sections of muscles are 

 examined, nerves of varying degrees of fineness may be seen, the 

 course of which is seldom parallel, but frequently at right angles, 

 to the direction of the fibres of the muscle. This is especially 

 noticeable in regard to isolated nerve fibres, and to the terminal 

 portions of such fibres. The muscles of different animals, and 

 even the several muscles of the same animal, are very unequally 

 supplied with nerves. In a few of the lower animals, as in 

 Bowerbankia, the muscles appear to possess as many nerve as 

 muscular fibres ; in others, especially in Fishes, there are sur- 

 prisingly few, whilst amongst the warm-blooded Yertebrata the 

 muscles of the eye, as a general rule, contain but few mora 

 muscular fibres than primitive nerve fibres. If we start with 



R 



