llf) 



THE TISSUES 



\'¥m^ 



muscle cell is flattened, and, in tissues rich in elastic fibres, e.g., 

 the media of some arteries, especially the aorta, is quite irregular 

 in shape. The central thickest part of each cell contains an elliptical 



or long rod-shaped nucleus. The 

 nucleus has a rather coarse intra- 

 nuclear network and one or more 

 nucleoli. | In some cells a centrosome 

 has been demonstrated. It lies out- 

 side and usually just to one side of 

 the nucleus. )j The irregular, wavy 

 and twisted nuclei often seen are 

 probably due to contractions of the 

 cytoplasm. The nucleus is sur- 

 rounded by an area of finely granu- 

 lar cytoplasm, most abundant at 

 the poles of the nucleus where it 

 frequently forms a little pointed cap. 

 The rest of the cytoplasm shows 

 delicate longitudinal striations, which 

 probably represent a longitudinal 

 arrangement of the spongioplasm. 

 These fibrils are extremely fine, are 

 frequently present in small numbers, 

 are not arranged in bundles, are ap- 

 parently homogeneous > and anisotro- 

 pic, and are often very difficult of 

 demonstration. \jThe fibrils lie in a 

 less differentiated cytoplasm. The 

 smooth muscle cell has no such dis- 

 tinct envelop as the sarcolemma of 

 striated muscle. The outer cyto- 

 plasm is, however, modified to form 

 a delicate cell membrane or at least 

 a modified surface layer. 



The cells are united by a small 

 amount of intercellular "cement" 



substance '/which reacts to silver 



i' 



nitrate, f Intercellular "bridges" 

 similar to those connecting epithelial cells have been described (Fig. 

 55), but are regarded by many observers as artefacts. By others fine 



Fig. 56. — Preparation of Smooth 

 Muscle Cells to show Fibrillar Struc- 

 ture. From intestine of Triton. 

 X 2300. (Heidenhain.) 



