x ELECTROMOTIVE ACTION IN NERVE 343 



It is undeniable that these marked differences exist. Unless 

 we assume (and in Biedermann's opinion there is no ground for 

 doing so) that the methylene-blue staining of the nerves in the 

 claw-muscles of the crayfish is in all cases very imperfect, the 

 most superficial comparison of two preparations of trunk- and 

 claw-muscles from the same animals, and similarly treated, is suf- 

 ficient to show the striking difference in the number of nerve encl- 

 branches. This expresses itself, on the one hand, in that the 

 terminal rarni traverse the whole interior of a muscle-bundle, 

 consisting of numerous larger and smaller groups of striated fibrils, 

 separated by sarcoglia, on the other by a far more copious branch- 

 ing of the several axis-cylinders. In contradistinction from these, 

 the motor endings in the muscles of the claw (as of the extremi- 

 ties) resemble those which are found in the lowest vertebrates. 

 In many respects the mode of arborisation and termination of the 

 nerves in the adductor muscle of the crayfish-claw is of especial 

 interest. It was stated above that the axis-cylinders, of which 

 there are always two of different size within the common sheath 

 of connective tissue, divide dichotomously and very freely, in such 

 a way that loth axis - cylinders invariably branch at the same 

 point, at each new bifurcation of the nerve-trunk, down to the 

 final endings (cf. Fig. 150). In the coarser branches the small 

 fibres are generally stained as a darker blue, while in the finest 

 terminal rami there is no apparent difference. These contain, 

 within a very thin sheath, two fine fibres of equal diameter, and 

 mostly highly varicose, which cross the direction of the muscle- 

 fibres, and at different points give off the true terminal branches. 

 These are also paired, and seem to end freely within the sarco- 

 plasmic mantle of the muscle-fibre. In rare cases these terminal 

 twigs also exhibit a scanty bifurcation. But there is never here, 

 or in the muscles of the extremities, any such rich plexus of 

 nerves as in the trunk-muscles. A similar type of muscular 

 nerve-endings is met with in insects also, the thorax-muscles of 

 the larger species of locust in particular giving with the same 

 method clear and elegant figures, which, in their abundance of 

 nervous ramifications, frequently recall the trunk -muscles of 

 Crustacea. But wherever there are well-marked Doyere's expan- 

 sions, the bifurcation of the ingoing axis-cylinders is markedly 

 localised, as in the end-plates of vertebrates. Thus in Hydro- 

 pliilus Biedermann found at most two knotty terminal branches 



