54 



THE MUSCULAK TISSUES 



cells which are either directly united by cement substance or are 

 held together by very delicate membranous lines of connective 

 tissue. In the former case adjacent cells are frequently connected 

 by very delicate protoplasmic fibrils, intercellular bridges. 



Each muscle cell (muscle fibre) consists of a much elongated 

 fusiform mass of finely granular cytoplasm which incloses a rod- 

 shaped nucleus. The peculiar shape of this nucleus, together with 

 its distinct nuclear wall and the distribution of its chromatin in 

 coarse granules, separated by wide intervals of achromatic sub- 

 stance, is characteristic of this variety of muscular tissue. These 



FIG. 55. SMOOTH MUSCLE FIBRES FROM THE PIG'S STOMACH, ISOLATED IN EQUAL PARTS 



OF ALCOHOL, GLYCERIN, AND WATER. Unstained. X 410. 



peculiarities of the nucleus in connection with the affinity of the 

 cytoplasm of the muscle fibres for certain acid dyes, e. g., eosin, 

 serve to distinguish this variety of muscle from white fibrous con- 

 nective tissue, with which it might otherwise be easily confounded. 



The cytoplasm of smooth muscle cells presents fine longitudinal 

 striations indicative of a subdivision into ultimate fibrillce, a re- 

 arrangement of the cell protoplasm which is more characteristic- 

 ally developed in the higher types of muscle. Transverse stria- 

 tions are not seen. The nucleus is found in the center of the cell. 



The surface of the cytoplasm is somewhat condensed, though a 

 true cell membrane, comparable to the sarcolemma of the striated 

 muscle cell, is wanting. The size of the smooth muscle cell is 



