288 SOLID PARTS OF ANIMALS. 



CHAPTER X. 



OF TENDONS. 



TENDONS are strong pearl-coloured bodies, which terminate 

 the muscles and attach them to the bones. They are known in 

 common language by the name of sinews. They are of very va- 

 rious forms, according to their situation. Some are narrow and 

 cord-like, as those which stretch across the wrist and ankle to 

 reach the fingers and toes. Others are compressed and strap- 

 shaped in the middle, and expanded at one or both extremities. 

 The tendo Achillis is convex on its cutaneous surface and flat on 

 the other, its fibres spreading out considerably where they run 

 into those of the muscle. The tendon of the plantaris is very 

 narrow and thin, but may be easily spread out to ten times its 

 natural breadth. 



Tendons are composed of fibres. They are very strong, and 

 are so firmly united to the muscle to which they belong, that, 

 when rupture takes place in consequence of any sudden and vio- 

 lent action, the tendon itself gives way, and not its junction with 

 the muscle. Tendons are smooth, and are covered externally 

 with a kind of loose sheath of cellular substance, which facilitates 

 their motion on other bodies. 



When a tendon has been softened in water, it may be spread 

 on the finger like a membrane, and has a silvery lustre. This 

 character enables us easily to distinguish the smallest tendons 

 from vessels and nerves. 



The fibres are longitudinal, and differ much in their appear- 

 ance from cartilage, but I am not aware that they have been ever 

 subjected to a microscopical examination. 



When put into boiling water, they swell, become yellow, and 

 semitransparent, and by long boiling they are dissolved and con- 

 verted into gelatin, which, on evaporation and drying, becomes 

 a firm glue. The transparency of the solution is impeded by 

 the presence of small vessels which float in it. 



If we plunge a tendon into concentrated acetic acid, it swells, 

 becomes transparent and gelatinous. At the same time its sur- 

 face becomes uneven, and is twisted in various directions, and 

 when cut it presents an annular and angular division, owing pro- 



