02 



NORMAL HISTOLOGY. 



bridges across the narrow intercellular spaces. The only tissue 

 with which this aspect of smooth muscular tissue is liable to be 

 confounded is dense fibrous tissue, as seen in the cross-sections of 

 tendons or ligaments (Fig. 69). There we also see polygonal areas 

 of various sizes, separated for the most part by only a thin layer of 

 cement. But these areas never contain nuclei, because they are 

 composed, not of cell-bodies, but of intercellular substance. The 

 nuclei of the flattened connective-tissue cells may be seen here and 

 there apparently lying within the cement, the body of the cell being 

 so thin as often to escape observation. These differences render it 

 easy to distinguish the two kinds of tissue in spite of their general 

 similarity when seen in cross-section. 



It is, of course, rarely that sections contain smooth muscular 



Fig. 76. 



Diagrams of smooth muscular fibres cut very obliquely. The explanation of Fig. 72, already 

 given, will make this one clear. In this case the outlines of the fibres in section will be 

 less sharply defined than in the preceding case, because, for instance, at the point a the 

 fibre a' is cut so as to leave only a thin edge, difficult of detection, and the fibre b has had 

 such a thin slice removed from it that the loss would be hardly perceptible. The appear- 

 ance of the section would, therefore, be much less easy of interpretation than is repre- 

 sented in the lower figure, where the outlines of the sections are equally distinct 

 throughout. 



tissue cut exactly in either of the directions just considered. In the 

 majority of sections that come under observation the muscle-fibres 

 are cut obliquely, and the oval or polygonal areas which result are, 

 therefore, elongated. The nuclei of the cells lie at an angle with 

 the line of vision, and, in consequence, appear foreshortened. If 

 now we focus the instrument so as to get a sharp image of the upper 

 surface of the section, and then rapidly turn the fine adjustment so 

 a- to bring the lower surface into focus, we shall notice an apparent 

 lateral motion of the nuclei and cell-sections. This apparent lateral 

 movement, due to change of focus, is an evidence of the elongated 

 shape and oblique position of the objects exhibiting it; and a little 

 reflection will convince the student that such oblique sections, when 



