10 STRUCTURE OF THE HUMAN BODY SKELETON. 



Achilles, which is inserted into the bone of the heel. The kind 

 of cords which are seen under the skin of the back of the hand 

 when the fingers are moved, are also finer tendons, which run 

 from the fingers to the muscles of the fore-arm. The tendons 

 are often confounded with the nerves, and it is said, for instance, of a 

 thin man making a great effort, that you can see the nerves 

 stretch under his skin ; but this is a mistake, it is the tendons 

 of his muscles which are seen. 



There is in the front of the arm a well-known muscle called 

 the biceps, the movements of which are very easy 

 to follow. To see it act well, it is simply necessary 

 to lift a tolerably heavy weight with the fore-arm 

 only by bending the elbow. The tendon which 

 connects the biceps with the bone of the fore-arm 

 may then be very well seen under the skin. We 

 also perceive that the muscle contracts and 

 thickens, at the same time, in proportion as the 

 fore-arm bends upon the elbow. This is really 

 how the muscles act : Attached by their extremities 

 to the bones of the skeleton, they contract at our 

 wish, and consequently cause the bones of the 

 skeleton to act upon each other. Each finger 

 has also tendons which are drawn up to extend it, 

 and drawn down to close it. Those men who 

 have the largest muscles are generally the 

 strongest ; but we frequently meet with very thin 

 people who are very strong, and they are then 

 said to be nervous, owing to the same error of 

 confounding the tendons with the nerves. We 

 generally judge of the strength of a man by the size of the 

 muscles of his chest, or the pectoral muscles. (See Diagram 1.) 

 It is these which assist in all forward motions of the arms. 



