THE LIMBS IN GENERAL AND THEIR PARALLELISM. 157 



Horse a rudiment of the crest dividing the ihac fossa into two parts, and in 

 some animals — the Pig, Sheep, and Goat — this crest, which is the trace of the 

 scapular spine, becomes constant and very evident. 



With regard to the cotyloid cavity, it repeats in the posterior limb the glenoid 

 cavity of the scapula. There remains to determine, in the latter bone, the 

 portions analogous to the ischium and pubis. If we rely upon the evidence 

 afforded by the nmscular insertions, we come to the conclusion that the ischimn 

 corresponds to the coracoid process, and the pubis to the clavicle of animals 

 which are provided with one. It will also be remarked that the coxa is directed 

 backwards, while the scapula inclines obliquely forwards ; this opposition in the 

 direction of the bones in no way alters their analogies ; the functions of the 

 members to which they correspond require this inverse position. 



Parallel between the femur and humerus. — The resemblance between these 

 two bones is remarkable. Thus there is found in the first. 1. An articular 

 head, better detached than that of the hmnerus, but shaped in the same manner. 

 2. A trochanter analogous to the great tuberosity, and also, like it, decomposable 

 into three distinct parts — smnmit, crest, and convexity. 2. A lesser trochanter, 

 representing the small tuberosity. 4. An eminence for the insertion of the 

 superficial gluteus muscle, which takes the place of the deltoid imprint, 5. An 

 inferior articular pulley continued between the two condyles by a non-articular 

 groove ; this trochlea certainly corresponds to the median groove of the inferior 

 humeral face. 



There are, no doubt, differences in the two bones, but they have no bearing 

 upon the result just indicated. Thus, the linea aspera of the femur is situated 

 behind ; that of the humerus in front. In the femur the two condyles of the 

 inferior extremity are placed behind the trochlea ; the contrary holds in the 

 humerus. These modifications are necessary, in order to give the movements of 

 the limbs a convenient direction. The leg is flexed backward on the thigh, while 

 the forear is flexed forward on the humerus. 



Parallel between the bones of the leg and those of the forearm. — It is more 

 particularly in these two regions that the. question of analogies has been resolved 

 in a contradictory manner by anatomists. It would have appeared less compli- 

 cated had it been studied in a large number of species. 



If we examine the leg-bones of certain Marsupials., in which the tibia and 

 fibula are apart as in the radius and ulna in Man, it will be found that : 1. These 

 two bones articulate w ith the condyles of the femur. 2. The anterior face of the 

 tibia has no ridge. 3. The patella is attached to the upper end of the fibula. 

 From this it might be concluded that, in Man and the domestic animals, the 

 tibia, with the exception of its anterior and external tuberosities, is the homologue 

 of the radius, and the fibula and external and anterior tuberosities of the tibia 

 are the homologues of the body and inferior extremity of the ulna. The patella 

 corresponds to the olecranon ; the mobility of the first cannot be offered as an 

 objection to this assimilation, for in Bactrians the olecranon forms, like the 

 patella, an independent bony nucleus. 



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

 analogy becomes so marked when these tw'o regions are compared, that it is 

 scarcely necessary to allude to them. 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 disrital bones are so much alike, that it is difficult to 

 distinguish the anterior from the posterior phalanges. 



