84 NATURAL THEOLOGY. 



say, under the ham, between the hamstrings, and within 

 the concave recess of the bone formed by the extuberances 

 on each s.Vle — m a word, along a defile, between rocks, pass 

 the great vessels and nerves which go to the leg.* Who led 

 these vessels by a road so defended and secured ? In the 

 joint at the sliouldcr, in the edge of the cup which receives 

 tlie head of the bone, is a Qiotch, which is joined or covered 

 at the top with a ligament. Through this hole, thus guard- 

 ed, the bloodvessels steal to their destination m the arm, in- 

 stead of mounting over the edge of the concavity. f 



III. In all joints, the ends of the bones which work 

 against each other, are tipped with gristle. In the ball-and 

 socket joint, the cup is hned and the ball capped Avith it 

 The smooth surface, the elastic and unfriable nature of car 

 tilage, render it of all substances the most proper for the 

 place and purpose. I should, therefore, have pointed this 

 out among the foremost of the provisions which have been 

 made in the joints for the facilitating of their action, had it 

 not been alleged that cartilage in truth is only nascent or 

 imperfect bone ; and that the bone in these places is kept 

 soft and imperfect, in consequence of a more complete and 

 rigid ossification "being prevented from taking place by the 

 continual motion and rubbing of the surfaces ; which being 

 so, what we represent as a designed advantage is an una- 

 voidable eilect. I am far from being convinced that this is 

 a true account of the fact ; or that, if it were so, it answers the 

 argument. To me the surmountmg of the bones with gristle 

 looks more like a plating with a different metal, than like the 

 same metal kept in a different state by the action to which 

 it is exposed. At all events, we have a great particular ben- 

 efit though arising from a general constitution ; but this last, 

 not being quite what my argument requires, lest I should 

 seem by applying the instance to overrate its value, I have 

 thought it fair to state the question which attends it. 



IV. In some joints, very particularly in the knees, th?re 



* Ches. Anat., p. 35. f Ibid. p. 39. 



