SYSTEMATIC ANALYSIS OP APPARATUS. 



83 



two cells might, and enough millions would exert all 

 the strength desirable. 



270. EXTENT AND STRENGTH OF MOTION ARE DETER- 

 MINED by the number of cells placed end to end and 

 side by side. 



271. Inf. ONE HUNDRED CELLS WILL BE REQUIRED 

 to produce at once the extent and strength of motion 

 for either of which alone ten cells would suffice. 



272. Form. IF A SERIES OF CELLS is FORMED INTO 

 A CIRCLE OR OBLONG, their contraction will diminish the 

 circle, and close or tend to close the orifice about which 

 they are placed. (See muscle around the eyes in Fig. 71.) 



273. IF RINGS FORMED OF CELLS BE PLACED BY THE 



SIDE OF EACH OTHER, a contractile tube will be formed, 

 and by the successive contraction and relaxation of its 

 rings, substances can be forced through it. (1, Fig. 70.) 



274. IF CELLS ALSO EXTEND LENGTHWISE the tube, 



it will be shortened ip length by their contraction. 

 .Fie. 79. IA FIG. 80. 



Fig. 79, a, represents the diagonal, b, the circular, and e, 

 the longitudinal fibres, formed of muscle-cells, in the (Eso- 

 phagus : that at 1, Fig. 80, opens into, the stomach, of which 

 5 is the outer coat, dissected and turned back from 7, 8, 9, 

 the muscular fibres, extending, as shown by the lines, in 

 different directions. 



270. By what -? 271. For what ? 272. What effect -? 273. What? 

 274. What if ? Describe Fig. 79. Fig. 80. 



