220 NATURAL THEOLOGY. 



knee-joint, for example, have every advantage of 

 greater strength without increased friction. 



Our author has perhaps dwelt sufficiently on 

 the smoothness given to the articulating surfaces 

 of the bones by the cartilages and the synovial or 

 lubricating fluid, vulgarly called joint-oil, (and ig- 

 norantly so called ;) and after these general obser- 

 vations, in order fully to comprehend the fine ad- 

 justment of each bone in its articulation, we should 

 require to go minutely into the anatomy. Then 

 we should find with how curious a mechanical 

 adaptation the motions are permitted in the pre- 

 scribed direction, and checked in every other. 

 We should be called to observe, also, how the mo- 

 tions of one joint are related to those of another ; 

 and how, by the combination of joints, each of 

 which is securely checked and strengthened, there 

 is a facility and extent of motioa produced by 

 their combination : for example, in the arm and 

 hand, where the motions are free, and varied in 

 every possible direction. 



It is interesting to see how the joints of the 

 lower extremities are modified in man in compa- 

 rison with those of the upper. We have else- 

 where remarked that the bones of the human pel- 

 vis, thigh, and leg, exceed those of all other ani- 

 mals in relative size, which shows a provision for 

 the erect position of man. The same is evinced 

 in the form of the joints, as the ankle, knee, and 

 hip ; for whilst their combinations give every ne- 

 cessary degree of motion consistent with security, 



