ANIMAL AND VEGETABLE 147 



The sarcomeres, or divisions, of muscular fibre are 

 shown thus 



and such a fibre consists of a number of these divisions, of 

 varying diameter and area, a is the dim, contractile 

 part, b the clear substance, and c Krause's membrane or 

 Dobie's line. We have it on the authority of Noel Paton that 

 the sarcolemma is " a delicate, tough, elastic membrane, 

 closely investing the fibre, and attached to it at Dobie's 

 lines.'' 



Sharpey's drawings of a portion of a human muscular 

 fibre, A, and of separated bundles of fibrils, B, are shown 

 on the next page. 



The motor nerves of voluntary muscle are efferent, and 

 therefore the impulse is from the brain, downwards. 

 Suppose, then, we connect these sarcomeres in series in a 

 battery circuit, thus : 



JSarffi 



Earth 



71. 



The law of electrical attraction would at once come into 

 play. The upper plate would induce electricity of equal 



