86 



NORMAL HISTOLOGY. 



FIG. 69. 



Diagrams illustrating the appearance of a longitudinal section of smooth muscular tissue. 



The distance between the lines A A and B B in the upper figure represents the thickness of 

 the section, the line A A being in the plane of its upper surface. The line C C in the lower 

 figure is in the plane of the transverse section represented in the upper figure. 



It will be noticed that only portions of the cells, h, a, d, c. and /, will be contained in the 

 longitudinal section (lower figure). The upper cut surfaces of those cells will appear as 

 oval areas when seen from above, h', a', d', c',f. Where the edges of those sections are 

 thin e.g., a the outlines of the corresponding oval (a') will be difficult of detection. 

 At the same time those portions of cells which lie at the top of the section will obscure 

 the outlines of the cells beneath. Thus, at the point 6 the outlines of the cells i and e 

 will be difficult of detection because covered by the cells k and a, and also because the 

 cell i overlaps the cell e. If the plane of junction were perpendicular to the surface of 

 the section, the outlines of i and e would be much more clearly defined. 



This brief analysis will serve to show that the outlines of the cells will rarely be seen with 

 distinctness in longitudinal sections of smooth muscular tissue. On the other hand, the 

 nuclei of the cells will be prominently visible in stained sections because of the color 

 they have received. For the recognition of this tissue, when so cut, we must, therefore, 

 depend chiefly upon the character and distribution of the nuclei. 



In order to avoid an unnecessarily complicated diagram, many of the cells represented in 

 the upper cut have been omitted from the lower figure. 



