122 ELEMENTS OF PHYSIOLOGY 



has the form of a very slender spindle, and contains one 

 nucleus (Figs. 27, 105). The fibers interlace and are held 

 together by fine connective tissue to make the hollow, 

 slow, involuntary muscles. 



210. Cardiac Muscular Tissue, of which the heart con- 

 sists, differs from both striated and plain muscular tissue 

 (Fig. 106). Its fibers possess one nucleus, like plain 

 fibers ; they are not spindle-shaped and narrow, however, 

 but broader and cylindrical. They are, moreover, faintly 

 cross-striated by light and dark bands. We may say, there- 

 fore, that although the heart is in every respect an involun- 

 tary muscle, it has more resemblance to striated than to 

 plain muscle. The many muscles used in breathing are at 

 times voluntary, and at other times involuntary ; but they 

 are all striated muscles with the usual structure. 



211. THOUGHT LESSON. Effects of Unhygienic Shoes. 



1. What the faults of shoes 

 may be (in shape, size, sole, heel, 

 toe, and instep). 



2. Deformities resulting to 

 foot (skin of foot, nails, joints, 

 arch, instep, and ankle). 



3. Effects of improper shoes 

 on habits of life. 



FIG. 107. - A Natural Foot. 4- Effect on particular organs 



or functions. 



5. Gain and loss to personal appearance from wearing 

 improper shoes. 



6. Effect on mind and disposition. 



7. If a shoe is too loose, it slips up and down at the heel 

 and chafes the skin there. If too tight, there is pressure 

 on the toes, which causes a corn or ingrowing nail. Have 

 your shoes been correct or have they been too loose or too 

 tight ? What proportion of people wear shoes that are too 

 tight ? 



