This constitutes the muscles, or the flesh, properly speaking. It is composed of elements called muscular fibres, which are of two sorts, the smooth, formed of fibre-cells, and the striped, formed of bundles of fibrils. The fibrils are the fundamental element of the muscular tissue; their primitive microscopic bundles unite in secondary bundles visible to the naked eye, and are known in descriptive anatomy under the name of fibres of the muscles. The fibrils are contractile but not elastic, and their primitive bundles have a homogeneous envelope of elastic but not contractile tissue called sarcolcmma.
Fig. 5. Striped muscular tissue as seen under the microscope.
a, Fibril deprived of the sarcolemma, to show the disks of which it is composed.
a', One of these disks.
b, Several fibres less magnified.
Fibrous Tissue has the same elements as the cellular tissue, united in compact bundles visible to the naked eye, strongly adherent among themselves, and interlaced in every direction. Fibrous tissue is found especially in the articulating and interosseous ligaments and in certain enveloping membranes, as the sclerotic, for example, which forms the white of the eye.
Tendinous And Aponcurotic Tissue is made up of a variety of very thin laminated fibres, with puckered edges, undulated and adhering directly at one extremity to the sarcolemma of the striped muscular fascicles, and to the osseous substance at the other. These fibres unite in little flattened polyhedral bundles, from .001 to .002 of a millimetre in breadth, from which the tendons and aponeuroses, which are of a tendinous nature, are formed. Tendinous tissue is inextensible lengthwise, and inelastic.