Textbook of normal histology: including an account of the development of the tissues and of the organs . uscu-lar fibres of the heart is very intimate; in manyplaces the vessels lie embedded within or even en-tirely surrounded by the muscular tissue (Meigs). Lymphatic vessels occur in striated musclein small numbers, but are entirely wanting inmany small muscles; when distinct lymphaticvessels do occur, they are confined to the largerand looser masses of the perimysium (Kolliker). The nerves supplying the striated muscleinclude the principal trunks which run within the perimysium, wherethey su
Textbook of normal histology: including an account of the development of the tissues and of the organs . uscu-lar fibres of the heart is very intimate; in manyplaces the vessels lie embedded within or even en-tirely surrounded by the muscular tissue (Meigs). Lymphatic vessels occur in striated musclein small numbers, but are entirely wanting inmany small muscles; when distinct lymphaticvessels do occur, they are confined to the largerand looser masses of the perimysium (Kolliker). The nerves supplying the striated muscleinclude the principal trunks which run within the perimysium, wherethey subdivide into smaller groups of medullated fibres, in order toreach the individual muscle-fibres; these latter receive their nervoussupply at certain points only, the nerves passing to the muscle toend in the special end-plates in the manner described more fullyin connection with the peripheral nerve-endings. The development of all varieties of muscular tissue is closelyrelated to the mesoderm, of which they are the direct plain or non-striated muscle is formed by the differentiation,. Injected voluntary mus-cle : the capillaries formrectangular-meshed net-works enclosing the indi-vidual fibres. 68 NORMAL HISTOLOGY. within certain areas, of the irregular mesodermic elements into theelongated fusiform fibre-cells. In suitable preparations all gradationsbetween the ordinary embryonal connective-tissue cells and themuscular elements may be observed, emphasizing the commonancestry of the two forms of tissue. Voluntary muscle, representing a higher specialization, is de-rived from definite areas constituting the inner layer of the muscle-plates, which are referable to theearly stages of the primary segmenta-tion into somites. The cells of themuscle-plate soon elongate, with pro-liferation of the nuclei, to become theprimitive muscle-fibres. These atfirst consist of greatly extended ele-ments, possessed of numerous nucleiand composed of granular indifferentprotoplasm.
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