688 ■ PHILOSOPHICAL TRANSACTIONS. [aNNO J 743. 



tual abrasion ; connected with strong ligaments, to prevent dislocation ; and 

 inclosed in a bag that contains a proper fluid deposited there, for lubricating the 

 two contiguous surfaces. So much in general. 



But if curiosity lead us a step further, to examine the peculiarities of each 

 articulation, we meet with a variety of composition calculated to all the varieties 

 of motion requisite in the human body. Is the motion to be free and exten- 

 sive in one place ? there we find the whole apparatus contrived accordingly. 

 Ought it to be more confined in another ? here we find it happily limited. In 

 short, as Nature's intentions are various, her workmanship is varied accord- 

 ingly. 



These are obvious reflections, and perhaps as old as the inspection of dead 

 bodies. But modern anatomists have gone further : they have brought the 

 articulations, as well as the other parts of the body, under a narrower inquiry, 

 and entered into the minutest parts of their composition. The bones have 

 been traced fibre after fibre ; but the cartilages have not hitherto been suffi- 

 ciently explained. After some fruitless attempts, by macerating and boiling 

 the cartilages in different menstrua, Mr. H. fell upon the method not only of 

 bringing their fibrous texture to view, but of tracing the direction and arrange- 

 ment of those fibres. 



Now, an articulating cartilage, is an elastic substance, uniformly compact, 

 of a white colour, and somewhat diaphanous, having a smooth polished sur- 

 face covered with a membrane ; harder and more brittle than a ligament, softer 

 and more pliable than a bone. 



When an articulating cartilage is well prepared, it feels soft, yields to the 

 touch, but restores itself to its former equality of surface when the pressure is 

 taken off. This surface, when viewed through a glass, appears like a piece of 

 velvet. If we endeavour to peel the cartilage off in lamellae, we find it imprac- 

 ticable ; but, if we use a certain degree of force, it separates from the bone in 

 small parcels ; and we never find the edge of the remaining part oblique, but 

 always perpendicular to the subjacent surface of the bone. If we view this edge 

 through a glass, it appears like the edge of velvet; a mass of short and nearly 

 parallel fibres rising from the bone, and terminating at the external surface of 

 the cartilage : and the bone itself is planned out into small circular dimples, 

 where the little bundles of the cartilaginous fibres were fixed. Thus we may 

 compare the texture of a cartilage to the pile of velvet, its fibres rising up from 

 the bone, as the silky threads of that rise from the woven cloth or basis. In 

 both substances the short threads sink and bend in waves on being compressed ; 

 but, by the power of elasticity, recover their perpendicular bearing, as soon as 

 they are no longer subjected to a compressing force. If another comparison 



