34 THE HUMAN .BODY. 



a simple mathematical precision, impossible to mistake, be- 

 cause all the surfaces are conceived and traced out geometri- 

 cally. In the joints, on the contrary, all the lines and surfaces 

 .are vague and uncertain; and when we examine an articular 

 extremity, the inferior extremity of the humerus for example, 

 we shall at first be tempted to believe that the unsymmetrical 

 projections and depressions, the incomplete grooves, and the 

 undefmable irregularity of the whole, belong to a work 

 spoiled or modelled at hazard by a confused mind; but on 

 seeing the action of the elbow-joint when laid open by the 

 anatomist, we discover that it is to this very irregularity of 

 the bony extremities, to the multiplicity of detail, to the 

 absence of symmetry, and to the more or less limited extent 

 of their articulating surfaces, that the variety of movement is 

 due, and we cannot sufficiently admire this assemblage, so 

 complex, but yet so justly calculated to give to the move- 

 ments of the fore-arm the greatest precision, strength, and 

 rapidity, and to combine these movements with those of the 

 arm and the hand. 



And if we pass from the most mobile of these joints to 

 those not at all or only slightly movable, the perfect coapta- 

 tion of their surfaces, their powerful methods of union, the 

 unity of movement of the bones, whether they take part in 

 the motion or serve only as fulcrums, all seem to be as 

 simple as possible in function, although the whole as well as 

 the details presents the most delicate application of the laws 

 of mechanics and statics. We may add that here as well as 

 everywhere in the study of the works of nature, we see the 

 organs develop themselves from the embryonic state to that 

 of perfection, under the influence and in the exercise of their 

 functions. . But leaving out the inimitable results produced 

 by life in natural creations, and considering them as inor- 

 ganic bodies, the mechanism of the joints leaves far behind 

 all the most ingenious productions of art or science. 



The distance appears to us greater still when, instead of a 

 combination of surfaces and the method of their union, we 

 .study, the action of the muscles and the transformations 

 which are incessantly taking place in the organs of digestion 

 and. respiration. In unveiling a part of these mysteries to 



