. Quain's elements of anatomy . minute varicose fibrilsthroughout the muscular substance,with which they are closely incor-porated. Moreover, another observer,Amdt, who, it is true, admits theexistence of the end-plate, describesin addition, a complex system of com-municating fibres which extendthroughout the muscular substance,and is the means of bringing theplate into connection with the musclecorpuscles and nuclei. These state-ments, however, have not hithertoreceived confirmation, although En-gelmann and Foettinger have beenled from observations upon insect-muscles to form a conclusion whi
. Quain's elements of anatomy . minute varicose fibrilsthroughout the muscular substance,with which they are closely incor-porated. Moreover, another observer,Amdt, who, it is true, admits theexistence of the end-plate, describesin addition, a complex system of com-municating fibres which extendthroughout the muscular substance,and is the means of bringing theplate into connection with the musclecorpuscles and nuclei. These state-ments, however, have not hithertoreceived confirmation, although En-gelmann and Foettinger have beenled from observations upon insect-muscles to form a conclusion whichis at least somewhat analogous, to the effect, namely, that the expansion of the nerve-fibres comes into actual con-tinuity with the isotropous substance of the muscular fibre. But the effect ofsection of a motor nerve in the living mammal—the resulting degenerationextending no further into the muscular fibre than the end-plate itself—is astrong argument against the existence of any such anatomical continuity. VOL. II. N. 178 NERVOUS SYSTEM. DEVELOPMENT OF NERVES. It has been shown by Balfour in elasmobranch fishes, and by Milnes Marshallin the chick, and the same is probably the case in mammals, that the nerve-roots andtheir ganglia, and in all probability the nerves generall y, develope as cell-out-growths from the rudimentary central nervous system. The latter, as has longbeen kn own, is formed by an involution of the ectoderm or epiblast along the middleline of the embryo. So that not only the nerve-cells and -fibres of the centralnervous system (brain and spinal cord), but also the peripheral nerves, and the nei-ve-cells of the ganglia in connection with them, are of ectodermal origin. No doubtthe connective tissue which enters into the construction of the nerves and nerve-centres, as well as the blood-vessels which are distributed in them, are mesodermal,having become formed as ingrowths from the surrounding mesoderm, but it is as yetuncertain whether this statement
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