SYSTEMATIC SYNTHESIS OF TISSUES. 175 



126. THE MUSCLE-CELLS ARE ESPECIALLY DIFFERENT 

 FROM THOSE OF THE SECRETORY TISSUE proper in this, 

 that the substance secreted in them is not of use in the 

 form in which it is secreted, but only when it is decom- 

 posed and destroyed as muscular tissue. 



127. MUSCULAR TISSUE is PASSIVE while it remains 

 muscular tissue, and as soon as it becomes active it 

 changes, for it is the change that produces the power of 

 activity or contraction. t 



128. SUCH TISSUE is NOT produced by the plant, nor 

 can it be ; it is the province of the animal to exhibit the 

 power developed by the plant, and to decompose what 

 the plant has compounded. 



129. THE CONTENTS OF THE MUSCLE-CELL exhibit all 

 the six elements of the first two groups ; but whether 

 the walls of the cell can secrete their contents from the 

 albumen of the blood directly, or whether it is necessary 

 that the albumen should undergo some process of pre- 

 paration, is not known ; but the latter is probably true. 



130. THERE ARE TWO FORMS OF MUSCLE-CELLS, that 

 of the striated and that of the non-striated. In the 

 former the cells are bead-shaped, and arranged end to 

 end (see Fig. 78) ; in the latter case the cells ta^er at 

 each end, and are sometimes found single and sometimes 

 clustered without regularity. 



131. THE USE OF THE MUSCLE-CELLS is to contract. 

 How the efiect is accomplished is not known, nor is the 

 rationale of the act even conjectured. It is certain that 

 each contraction is attended with a corresponding 

 amount of decomposition of muscular secretion, to be 

 renewed only by a corresponding amount of substance 

 eaten. 



132. IT is ALSO CERTAIN that there is no other power 

 so economically used as the power of the muscle-cells. 



133. IF THE SOURCE OF THIS POWER IS TRACED BACK 



126. How -? 127. When -? 128 What said ? 129 What said -? 

 130. What - ? Describe Fig. 78. 131. What 132. What- ? 133. What said? 



