TENDONS, APONEUROSES. 



37 



in right lines ; or by the insertion of the fleshy fibres at some 

 point in the length of the tendon, at various angles, but never 

 exceeding 45 degrees. Such is the 

 force of this adhesion between the 

 two tissues that rarely if ever does 

 external violence or the greatest 

 effort succeed in overcoming it, the 

 tendon or the muscle breaks before 

 separating at their points of union. 

 We have already pointed out, in 

 speaking of the articular ligaments, 

 the remarkable fact that the adhe- 

 sion of two organic tissues is strong- 

 er than the cohesion of either of 

 the respective tissues. 



The tendons and the aponeur- 

 oses, though very flexible, are en- 

 tirely inextensible, and offer there- 

 fore great resistance to force 

 applied to their length. This is 

 one of the conditions necessary for 

 the part which they play in uniting 

 the organ of motion and the object 

 to be moved. 



Like the ossifying cartilages, the tendons may be considered 

 as a transition tissue. They partially ossify with age at their 

 points of insertion into the bones, but they are never entirely 

 transformed in the human race, as in some animals, the 

 Gallinaceae for example, into a bony trunk. Suppleness and 

 variety of movement would not accord with this transforma- 

 tion; and among the differential marks which Plato might 

 have added to his famous definition of man, this would have 

 sufficed to prevent Diogenes from saying, as he exhibited the 

 cock stripped of its feathers, "Behold Plato's man!" 



A relatively slender tendon suffices to transmit a motive 

 force developed by a certain amount of contractile fibre, and 

 the fleshy portion of the muscles far surpasses in volume the 

 tendons and the aponeuroses. If the muscular fibres attached 

 themselves directly to the bones the surface of the bones 



Fig. 14. Lower portion 

 of the leg. 



A. Tendon of Achilles. 



