MODE OF TERMINATION OF MOTOR NERVES IN AMPHIBIA. 211 



muscles as, for example, the sartorius many fibres may be 

 found which present several such spots, whilst in the shorter 

 fibres of the gastrocnemius, as a rule, only one nerve eminence 

 is visible. In specimens prepared in this way the continuity 

 of the nerve sheath of Schwann with the sarcolemma may be 

 observed in profile, without any further manipulation. 



In order to bring the termination of the nerves in the fresh, 

 still living, and contractile muscle into view as in the Arthro- 

 poda the fibres of the gastrocnemius are to be isolated. In 

 the broken-up and separated muscle the course of the finest 

 nerve twigs, as they cross the fibres at right angles, may be 

 followed without difficulty by the pigmented vessels that ac- 

 company them. In this region the terminal branches are given 

 off; and if a few muscular fibres are raised with the forceps, 

 after the tendinous fasciculi to which they are attached have 

 been divided at both extremities, in all probability the desired 

 appearances will be presented to the eye. The specimen so 

 obtained may be examined, either without any addition or in 

 a 0*5 per cent, solution of chloride of sodium, in which the 

 muscle long retains its excitability. The aqueous humour 

 and the serum of the blood of the frog may also be employed. 

 Just before the nerve traverses the sarcolemma it usually 

 undergoes division, forming the so-called terminal brush (leash 

 or pencil) of the nerve, the extremely short branches of which 

 seldom exceed in length the transverse diameter of the mus- 

 cular fibre, and may lie in all conceivable directions to its axis. 

 The number of branches of the first order rarely exceeds five ; 

 those of the second order may amount to ten or twelve. The 

 medullary investment and the sheath of Schwann accompany 

 the nerves up to the very point of their attachment to the 

 muscular fibre, but here the medullary sheath terminates 

 abruptly, and without marked attenuation. In profile views 

 no kind' of distinction is to be perceived between the contour of 

 the sarcolemma and that of the membranous sheath ; indeed, 

 the flat and granulated nuclei of the latter can not unfre- 

 quently be followed into that part which all would acknow- 

 ledge to be true sarcolemma, and which, as is well known, is 

 in the frog destitute of nuclei. No better evidence than this 

 can be offered in regard to the continuity of the two tubes. 



