130 NATURAL THEOLOGY. 



the body, let it consist of what it will, substance s 

 restored, and waste repaired.^ 



Movable joints, I think, compose the curiosity 

 of bones ; but their union, even where no motion 

 is intended or wanted, carries marks of mechanism 

 and of mechanical wisdom. The teeth, especially 

 the front teeth, are one bone fixed in another, like 

 a peg driven into a board. The sutures of the skull 

 are like the edges of two saws clapped together in 

 such a manner as that the teeth of one enter the 

 intervals of the other. We have sometimes one 

 bone lapping over another, and planed dow^n at the 



^ This subject is touched upon in the Appendix, in treating of 

 the spine. We may here take a practical illustration. We have 

 said that exercise is necessary to the perfection of a joint. Sup- 

 pose the knee-joint to be inflamed : it is of course kept in perfect 

 rest, because motion produces pain. This absolute rest, joined 

 with inflammation, alters all the textures ; the bone becomes light 

 and spongy ; the cartilage is absorbed ; the ligaments which ought 

 to hold the bones together become loose and relaxed ; and what 

 the surgeon calls consecutive dislocation may take place — that is, 

 the bones will actually shift their place, from the defect of those 

 attachments which ought to keep them together. JNow, let us sup- 

 pose the inflammation to have subsided : by due attention all may 

 be restored ; and by no other mode than moving the joint — the 

 only precaution necessary being, that it shall be moved with a care 

 and gentleness corresponding to its weakened condition. By this 

 simple means the ligaments will acquire firmness, the cartilages 

 smoothness, and the synovia, or lubricating mucilage, will be again 

 poured out : from all which we see, that in the living animal tex- 

 tures, wear and tear do not take place upon continued motion ; but, 

 on the contrary, that exercise is made the stimulus to improvement. 

 All other proofs of design, as adjustment, relation, compensation, 

 prospective contrivance, are weak in comparison with this. 



