AND PHYSIOLOGY. 



137 



268. Contraction commences at one End — Only a Part 

 of the Fibrils in a State of Contraction at Once. — The 

 contraction of a muscle does not take place in all parts of the 

 fibers at the same time, but commences at one end, and con- 

 tinues through in regular F ia , 152. 



order, as is seen in the 

 cut 152. It is also sel- 

 dom the case that all the 

 fibers are contracted at 

 once. This explains the 

 reason why insane people 



« , . . , Muscular Fiber contracting, a, Uncontracted 



are Olten SO prodigiously part. &, Contracted part. 



strong, since the whole of the muscle is made to act at once. 

 It also shows us why we can keep a muscle contracted for a 

 long time, as in carrying a weight for a long distance, and 

 also why a short and violent muscular action weakens and 

 tires us more than a protracted and more moderate one. The 

 simple explanation is, that but a part of the fibrils are con- 

 tracted at once, and when the nervous force is exhausted from 

 one set of fibrils, a new set are called into action to supply 

 their power. 



269. Examples of Mnscular Strength— As examples of 

 great muscular strength, we have given to us the history of a 

 Samson and Goliath. And in more modern times we read of 

 Milo of Crete who killed an ox with his fist, and then carried 

 it more than 600 feet. He also saved the life of his fellow- 

 scholars and teacher, Pythagoras, by supporting the falling 

 roof until they had time to escape. Another man is men- 

 tioned who could raise 300 pounds by the muscles of his lower 

 jaw. This strength, however, is exhibited much more strik- 

 ingly in another part of this chapter under the head of Com- 

 parative Myology. 



268. Do all the fibers, or even all portions of each fiber act at once in ordinary cases ? 

 Instance insane people. 269. Give examples of great muscular strengh as illustrated by 

 Goliah and Milo. 



