36 . SCIENCE PRIMERS. [§ in. 



vessels only, you would have brought about very 

 nearly the same effect. We saw in the last lesson 

 how all parts of the body are supplied with blood- 

 vessels, with veins, and arteries. In the arm there 

 is a very large artery, branches from which go all over 

 the arm. Some of these branches go to the biceps 

 muscle. What would happen if you tied these 

 branches only, tying them so tight as to stop all the 

 blood in them, but not interfering with the bluod-vessels 

 in the rest of your arm ? The arm as a whole would 

 grow neither pale nor cold, it would not become clumsy 

 or heavy, you would not lose your feeling in it, but 

 nevertheless if you tried to bend your arm you would 

 find you could not do it. You could not make the 

 biceps contract, though all the rest of the arm might 

 seem to be quite right. 



Wliat does this teach us ? It teaches us that 

 the power which a muscle has of contracting 

 when called upon to do so, may be lost and 

 regained, and that it is lost when the blood 

 is prevented from getting to it. When a cord 

 is tied round the whole arm, the power of the whole 

 arm is lost. This loss of power is the beginning 

 of dejith, and indeed if the cord were not unloosed 

 the arm would quite die — ^would mortify, as it is 

 said. When only those blood-vessels which go to 

 the biceps are tied, the biceps alone begins to die, all 

 the rest of the arm remaining alive, and the first sign 

 s of death in the biceps is the loss of the power to 



contract when called upon to do so. 

 5 In order that you may bend your arm, then, 

 ^^ you must not only have a biceps muscle with its 

 nerves, its tendons, and all its arrangements of bones 



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