. Electro-physiology. Electrophysiology. X ELECTROMOTIVE ACTION IN NERVE 339 reach the contractile substance; the medullary sheath, as a rule, terminates shortly before the definite ending. Stress must be laid upon the much-disputed fact of the passage of the axis- cylinder, since, admitting certain premises as to the nature of the propagation of a stimulus, the sarcolemma would offer no absolute hindrance. The axis-cylinder seldom remains entire, but exhibits a more or less copious arborisation (Kiihne's terminal arborisation], " hypolemmal" in situation, and occurring according to
. Electro-physiology. Electrophysiology. X ELECTROMOTIVE ACTION IN NERVE 339 reach the contractile substance; the medullary sheath, as a rule, terminates shortly before the definite ending. Stress must be laid upon the much-disputed fact of the passage of the axis- cylinder, since, admitting certain premises as to the nature of the propagation of a stimulus, the sarcolemma would offer no absolute hindrance. The axis-cylinder seldom remains entire, but exhibits a more or less copious arborisation (Kiihne's terminal arborisation], " hypolemmal" in situation, and occurring according to two types, (a) in amphibia (Fig. 222), (6) in reptiles, birds, and mammals. The former presents tolerably straight, rounded, or flattened terminal branches, running parallel with the axis of the muscular fibre ; these extend widely for some little distance close under. FIG. 222.— Arborisation from frog's gastrocuemius. (Kiihne.) the sarcolemma, and always end distinctly in a blunt point. Here and there they bear long, oval nuclei, which Kiihne termed " ; In contrast with these " branches " are the " plates " of other vertebrates, where the rarni take a bending and intricate course, or form laminal, lobed expansions within a small circular or oval " field of innervation," that rarely comprises the whole muscle-fibre (Figs. 223-225). It is characteristic of these "end- plates " that they nearly always present a more or less conspicuous accumulation of finely-granulated substance set with nuclei (sarcoplasm), within which are embedded the ramifications of the axis-cylinder (Kiihne's " end-plate" Fig. 224). In the branched form this " granulosa " is seldom perceptible, while in the plates it is frequently well-developed and appears in profile as a projecting expansion, corresponding with Doyere's expansion in insect-muscle (Fig. 225).. Please note that these images are extracted from scanned page image
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