11-j '//// BOXES 



more particularly in these fcwo'tfegkxM that the question of analogiei has 

 been resolved in -a contradictory manner by anatomists. It would Imvi: 

 appeared less complicated had it been studied in a largo number of spec it s. 



It lias been pretended that the patella and the upper part of the tibia 

 represent the superior extremity of the ulna and radius; and that tin: 

 inferior portion of the ulna is represented by the fibula, and the lower part 

 of the radius by that of the tibia. This opinion is erroneous. It is true 

 that in Man the tibia and patella articulate with the femur, as the superior 

 extremity of the ulna and radius responds to the humerus. But in quad- 

 rupeds, whoso thoracic members are destined to sustain the weight of the 

 body, this disposition is no longer observed ; the radius is seen to give 

 support to all the humeral surface, just as the tibia receives the femoral 

 surface; and, besides, the ulna becomes only a simph: complement to the 

 elbow articulation, as the fibula does to the femoro-tibial articulation. 



The tibia, therefore, corresponds to the radius, and the fibula to the ulna. 



The olecranon is represented by the superior nucleus of the fibula, and 

 not by the patella. The latter bone is nothing more than a kind of scsainoid, 

 intended to facilitate the action of the extensor muscles of the leg. It 

 might be objected to this comparison that, in the anterior limb, the extensor 

 muscles are attached to the olecranon. But we reply that it matters little 

 where the muscles which move the leg or arm are fixed on one or other 

 of the two bones of these regions, because these bones act conjointly in the 

 movements of flexion and extension. 



Parallel between the bones of the posterior and those of the anterior foot. 

 The analogy becomes so marked when these two regions are compared, that 

 it is scarcely necessary to allude to it. The tarsal bones are to the posterior 

 limb what the carpals are to the anterior one; it is even possible to compare, 

 one by one, the several pieces in these regions. The metatarsals are but a 

 repetition of the metacarpals ; while the digital bones are so much alike that 

 it is difficult to distinguish the anterior from the posterior phalanges. 





CHAPTEE III. 



THE BONES IN BIRDS. 



THESE animals, destined for the most part to sustain themselves in the air, should 

 exhibit in the conformation of their skeleton all the conditions which may favour it-rial 

 locomotion; from this arise the differences which distinguish their skeleton from that 

 of mammalia, differences which will now be rapidly traced. 



VKRTEBRAI. COLUMN. Cervical vertebra: . The cervical stalk represent* in the bird. 

 as in the mammal, a kind of balancing pole curved like an S, which snpi>orts tli<- IK ail, 

 and by its changes of form and direction varies the centre of gravity. When a bird 

 rises in the air and flies rapidly, it lengthens the neck and stretches out the heail i . 

 carry the centre of gravity forwaids. IJut when it rests on tin- Around, it makes the 

 balancing-pole assume the natural nnd more or less giacet'id inflection. by tin-owing the 

 head backwards, and transferring the greater portion of the weight of its lxly to the 

 columns of support formed by the posterior members. These di.-pla<-ements of the centre 

 of gravity are executed in birds on n more extensive scale than in mammalia ; the 

 vertebral stalk in the former is also longer, lighter, and enjoys an excessive mobility. 



The vertebrae composing it number fourteen in fowl*, twelve in tlie piijeon, fifteen in 

 the duck, and eighteen in the tfoogf. ; in the nwan twenty-three have been counted : a 

 curious variety which singularly contrasts with the numerical unity noticed as one ot 

 the most remarkable characters in mammalia! These vertebra? are generally longer 

 than in the latter class, and are particularly distinguished by the configuration of the 



