H8 ELEMENTARY ZOOLOGY. 



substance in muscle and the different fibres are bound together by 

 connective tissue. 



There are two main types of muscle cells found in the higher 

 animals: (i) plain muscle (Fig. 8; 13), and (2) cross-striate muscle 

 fibres (Fig. 2 5, mf) . The latter are more highly organized and are 

 more efficient and prompt in their action. In general, those muscles 

 that are directly under the control of the brain, as the muscles that 



FIG. 24. Bony tissue, shown in cross section, h, Haversian canal, containing an 

 artery (a) and a vein (v), lymphatic spaces, and nutritive cells; c, canaliculi; /, lacuna; 

 la, a plate of bony intercellular substance lying between rows of bone cells (/). 



Questions on the Figure. What is the difference between figures 

 A and B? How does bone compare in appearance and in work 

 with the other supportive tissues? How is its intercellular sub- 

 stance laid down? Of what is it composed? How are the cells in 

 the bone nourished? How -do they come to lie in the solid bone? 

 What changes occur in this type of tissue with age? What is the 

 function of the Haversian canals? Of the canaliculi? 



move the skeleton, are of the cross-striate kind. Those which 

 produce contraction in the stomach, intestines, and othe. organs 

 not under control of the higher nerve centres are of the plain variety. 

 The fibres are bound together by connective tissue into bundles 

 and these into larger bundles, and thus muscles are formed. 



130. The Nervous Tissues. Nervous tissues are closely related, 

 on the one hand to the sensory epithelium of the skin and elsewhere, 

 and on the other to the muscular tissue. Through the former they 



