4 20 MOVEMENTS 



particularly in muscles that are habitually exercised (see Plate IX, 

 Fig. 6). The muscular substance, presenting this peculiar striated 

 appearance, is enclosed in a thin but elastic and resisting tubular 

 membrane, called the sarcolemma or myolemma. This envelope can 

 not be seen in ordinary preparations of the muscular tissue ; but it 

 frequently happens that the contractile muscular substance is broken, 

 leaving the sarcolemma intact, which gives a good view of the mem- 

 brane and conveys an idea of its strength and elasticity. Attached to 

 the inner surface of the sarcolemma are small elongated nuclei with 

 their long diameter in the direction of the fasciculi. 



Connective Tissue. In the muscles there is a membrane surround- 

 ing a number of the primitive fasciculi. This is called the perimysium. 

 The fibrous membranes that connect together the secondary bundles, 

 with their contents, are enclosed in a sheath enveloping the entire 

 muscle, sometimes called the external perimysium. The peculiarity of 

 these membranes as distinguished from the sarcolemma is that they 

 have a fibrous structure and are connected together throughout the 

 muscle, while the tubes .forming the sarcolemma are structureless and 

 each one is distinct. 



The name usually given to ordinary fibrous tissue is connective 

 tissue. It has been called cellular, areolar or fibrous, but most of these 

 names were given without a clear idea of its structure. Its principal 

 anatomical element is a fibre of excessive tenuity, wavy and with a sin- 

 gle contour. These fibres are collected into bundles of variable size 

 and are held together by an adhesive amorphous substance. The wavy 

 lines that mark the bundles of fibres give them a characteristic appear- 

 ance (see Fig. 81). 



The direction and arrangement of the fibres in the various tissues 

 present marked differences. In the loose tissue beneath the skin and 

 between the muscles and in the loose structure surrounding some of the 

 glands and connecting the sheaths of bloodvessels and nerves to the 

 adjacent parts, the bundles of fibres form a large network and are wavy 

 in their course. In the strong dense membranes, as the aponeuroses, 

 the proper coats of many glands, the periosteum and perichondrium and 

 the serous membranes, the waves of the fibres are shorter and the fibres 

 themselves interlace much more closely. In the ligaments and tendons 

 the fibres are more nearly straight and are arranged longitudinally. 



The proportion of elastic fibres in different situations is variable ; 

 but they are all of the smallest variety and present a striking contrast 

 to the inelastic fibres in form and size. Although they are very small, 

 the elastic fibres always present a double contour. 



Certain cellular and nuclear elements are always found in the con- 



