Human Physiology. 



shortens the whole muscle, which becomes thick in proportion 

 as it shortens, as may be seen in the contraction of the biceps. 

 Butchers' meat is composed of muscle, intermingled with fat, 

 blood vessels, nerves, and connective tissue. There are about 

 five hundred muscles in the human 

 body, to carry on all its movements. 

 A large number are employed to 

 hold the head erect, and give it its 

 various movements. A section of the 



neck (Fig. 20) shows all these muscles Fig I9 ._ M uscu L AR 

 cut across, and sections of the fore-arm FIBRE, dividing into fib- 

 er calf of the leg would show a similar rillss, magnified 300 

 number. diameters. 



Many of these muscles are in constant action, conscious or 

 unconscious. The heart, a collection of very powerful muscles, 

 beats on from the first signs of life in the foetus till death no 



Fig. 20. TRANSVERSE SECTION OF 



THE NECK. 

 12. Trachea. 13. Esophagus. 



Fig 21. MUSCLES OF THE FACE, 



pause, no rest. If the heart beat only sixty times a minute, its 

 beats in a man of seventy count over two thousand millions. 



