ON STATICS. 99 



is little if at all diminished : when it relaxes itself, it is merely passive, for 

 the fibres, being extremely flexible, can have little or no efl&ct in separating 

 the parts to which they are attached ; this separation is generally performed 

 by the action of other muscles which are called the antagonists of the first, 

 but sometimes by elastic ligaments, or by other means. The bone forms a 

 lever of the second kind, where the two forces opposing each other are on 

 the same side of the fulcrum. In general the insertion of a muscle is much 

 nearer to the fulcrum than the point of action, and the obliquity of its 

 direction gives it a still greater mechanical disadvantage with regard to 

 rotatory power ; but it is more convenient in the animal economy to pro- 

 duce a great contractile force than a great extent in the original motion. 

 For instance, when the arm is raised by the exertion of the deltoid muscle 

 of the shoulder, a very strong contraction takes place in the muscle, but 

 the action is only continued through a short space ; had the contractile 

 power been weaker and more extensive, the shoulder must have been made 

 higher, in order to give it sufficient purchase, and the projection would 

 have been inconvenient. 



Borelli* has calculated that the immediate force of the biceps, or double- 

 headed muscle which bends the arm, is equivalent to about 300 pounds, and 

 that of the muscles which raise the lower jaw, above 500 in man, but in 

 beasts of prey far greater. It is obvious that in muscles of the same kind 

 the strength must be as the number of fibres, or as the extent of the surface 

 which would be formed by cutting the muscle across ; and it is not im- 

 probable that the contractile force of the muscles of a healthy man is 

 equivalent to about 500 pounds for each square inch of their section. The 

 weakest man can lift with his hands about 125 pounds, a strong man 400. 

 Topham, a carpenter, mentioned by Desaguliers, could lift 800 pounds. 

 He rolled up a strong pewter dish with his fingers ; he lifted with his teeth 

 and knees a table six feet long, with a half hundred weight at the end. 

 He bent a poker, three inches in circumference, to a right angle, by striking 

 it upon his left fore arm ; another he bent and unbent about his neck ; and 

 snapped a hempen rope two inches in circumference. A few years ago 

 there was a person at Oxford who could hold his arm extended for half a 

 minute, with half a hundred weight hanging on his little finger. A young 

 gentleman, who has distinguished himself as a pedestrian by going 90 miles 

 in 19 hours, has also lifted two hundred weights, one in each hand, and 

 made them meet over his head. 



Sometimes feats of strength apparently extraordinary have been ex- 

 hibited by men who have not really been possessed of any material supe- 

 riority. Desagulierst relates, that one of them used to withstand the force 

 of two horses drawing at a girdle passed round his middle, while his feet 

 acted on a firm obstacle. By falling suddenly backwards, in an oblique 

 position, he broke a rope which was fixed a little before his feet. He 

 supported one or two men by forming his body into an arch ; and by a 

 harness fitted to his hips, he sustained a cannon weighing two or three 



* De Motu Animalium, 4to, Lugd. Batav. 1710, p. 30 et seq. 

 f Course of Experimental Philosophy, 2 vols. 8vo, Lond. 1763, i. 266, &c. 



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