SS Comparative Analomy ; or an Attempt at 



which if followed up and clos'ely investigated might perhaps 

 lead to a discovery of the causes of motion. 

 • I shall now turn to the bone of the animal and wood of the 

 vegetable, which may from some curious particulars be com- 

 pared together. The first has a skeleton or system of bones 

 which gives firmness and shape to t!ie fabric, keeps the soft parts 

 in their places, affords fixed points to the organs of motion, and 

 gives them their proper direction, and jjrotects some of the most 

 tender parts from external injurv. To connect the bones to- 

 gether, there are Uganitiils ; and to afford smooth surfaces for 

 them to play easily on one another^ their extremities are fur- 

 nished with cartHages or gristle. The bones consist of an in- 

 terior, which is a sjjecies of honeycomb, and an exterior surface, 

 which has many I'di/ers formed in a particular manner ; the last 

 if cut witii a very sharp knife, and very thin, appears composed 

 of many meandering vessels ji?//«c? 2vil/i atoms, which seem to be 

 rather sol'/dy from the clear spaces thev show between them ; 

 while the honeycomb parts are plates, thick in the middle and 

 meeting in their t/iin edges. This is also the same as the for- 

 mation of the large bones of the skull, which increase also to- 

 wards their centres ; but the most extraordinary part of the 

 wood is, that the foundation exactly resnilles the thin surface 

 of the bone, and is really composed of diminutive vessels filled 

 with atoms : but this is only to be ste/i in loth when excessively 

 1/iasni/ied, then they exactly resemble each other. But the sy- 

 stem of wood, though it gives firmness to the fabric, yet obeys 

 most strictly the luivs of the line of life in its siiape : it pre- 

 serves, however, this important jiart from injury, but is within 

 every other soft ingredieul, and therefore cannot defend it. 



In trees and shrubs it serves as some support to the muscle, 

 but in annuals and Iierbaceous plants the muscle changes its 

 place, and is at the external pen t of the ivood. It cannot be 

 said to afford a fixed point for the organs of motion; for it is the 

 gristle which does this, which forms the brills round which the 

 spiral winds itself, and which covers the ends of the wood in 

 such a manner as to enable them to slip over or into each other, 

 like a cup and ball. I never saw the knee or elbow of a human 

 skeleton that it did not remind me of a Galium, Selene, or some 

 of the stems of those plants which swell at the joint. It is a 

 sort of gristle which serves this purpose and sheathes the wood, 

 a kind of tin k inatter, which performs, in its solid or liquid 

 state, many important functions in the vegetable oeconomy, and 

 makes a part, I doubt not, of that resinous compound Dr. Thom- 

 son discovered in the wood. 



But how curious .'t would be to possess and be able to exa- 

 mine that liquid which performs that extraordinary office of 



clearing 



