OSSEOUS SYSTEM. (Co M p. ANAT.) 



portion of the skeleton into an osseous frame- 

 work able to sustain the stress of those power- 

 ful muscles that wield the instruments of 

 flight. At one end each of these pieces 

 is moveably articulated with the distal ex- 

 tremity of the corresponding dorsal rib, whilst 

 at the opposite it is firmly attached to the sides 

 of the expanded sternum by joints that admit 

 of a certain extent of motion. 



It is in the Chelonian Reptiles that these 

 accessory portions of the thorax attain their 

 greatest growth, spreading into broad plates 

 that are connected by strong sutures to the ex- 

 tremities of all the spinal ribs and likewise to 

 each other in the Tortoises, completing thus 

 the carapax or dorsal shield ; and, moreover, 

 being solidly united at the sides with the enor- 

 mous apparatus of sternal bones, the whole 

 body of the Tortoise becomes encased in bony 

 armour, derived entirely from the thoracic 

 elements of the skeleton. 



The ANTERIOR LIMBS of Vertebrate animals, 

 although essentially composed of similar ele- 

 ments throughout all the classes belonging to 

 this great division of animated nature, are 

 made subservient to very various and opposite 

 uses; the pectoral fin of the Flying Fish, the 

 enormous hand of the Skate, the paddle of 

 the Turtle, the flipper of the Whale, the wings 

 of the Bird and of the Bat, the broad shovels 

 of the Mole, and that masterpiece of organiza- 

 tion, the human hand, being respectively but 

 simple modifications of the same structure. 



In the osseous Fishes, indeed, it is not 

 always easy to recognise the elements that are 

 correlative with those of the higher Vertebrata; 

 but a little attention is sufficient to prove the 

 construction of the pectoral fins among the 

 finny tribes to be true representatives of the 

 anterior extremities of other races, as will be 

 evident from the following masterly analysis of 

 the parts composing the pectoral fin of the 

 Perch, given in Cuvier's great work on Fishes. 

 Immediately behind the gill-openings there is 

 placed on each side a framework of bones 

 that bound the branchial apertures. This frame 

 is attached superiorly to the back of the head, 

 but inferiorly the two halves are united together, 

 forming a bony zone that surrounds the body 

 at this part ; and being connected inferiorly 

 with the body of the os hyoides, forms here a 

 kind of isthmus that separates the gill-open- 

 ings from each other. The bony zone above 

 described is made up on each side of three 

 pieces, which represent the bones of the 

 shoulder and of the arm, to which is affixed 

 posteriorly a group of two or three other bones 

 that represent the forearm, wherewith is con- 

 nected the fin itself, the representative of the 

 hand. The names applicable to these pieces 

 of the skeleton when their analogies are strictly 

 investigated are as follow : The suprascapular* 

 the scapular,-]- the humerus,l the radius and ulna, 



* Synonyms Omoplate, Omolite, Pcdicule de 

 I'epaule. 



t Syn. Om0plate(GeaBToy'),Acromion( Baltkor). 



t Syn. Clavicle (Meckel, Geoff.), Cmnusteoii 

 (flakier). 



839 



to which succeed the carpal bones and the 

 phalanges of the fin. In addition to these must 

 be noticed the two pieces regarded by Cuvier 

 as representing the coracoid bone of Reptiles. 



When fully developed, the anterior extremity 

 is made up of a greater number of elements 

 than exist in the human skeleton. The shoulder 

 is a strong framework, composed of three dis- 

 tinct pieces, named respectively the scapula, 

 the clavicle, and the coracoid bone. The other 

 bones of the limb resemble each other in their 

 general arrangement throughout all the Verte- 

 brata, and in the Crocodile, where all parts of 

 the limb present a medium state of develope- 

 ment, the analogies between the bones com- 

 posing it and those of the human arm are at 

 once recognised. The humerus, a single bone, 

 supports the first division of the limb. Two 

 bones, the radius and the ulna, are met with 

 in the forearm, while the bones of the carpus, 

 the metacarpus, and the phalanges of the fingers 

 present an arrangement similar to what is found 

 in the human body. In order, however, to 

 appreciate the important modifications required 

 in the disposition and conformation of these 

 elements in the different races possessing them, 

 it will be needful to examine them successively 

 in the order in which they have been enu- 

 merated. 



The scapula is the most important piece 

 entering into the composition of the shoulder, 

 and not unfrequently, among the Mammiferous 

 races, is the only bone developed for the sup- 

 port of the anterior limb. In Reptiles and in 

 Birds, where so great freedom of motion as is 

 required in terrestrial Quadrupeds would be 

 inadmissible, the movements of this part of 

 the skeleton are considerably restricted, and a 

 kind of anterior pelvis formed which gives 

 great strength and firmness to this part of the 

 skeleton. The scapulae are generally laid like 

 splints along the exterior of the chest, in which 

 position they are, as it were, suspended by 

 strong muscles ; but frequently this arrange- 

 ment is necessarily departed from for obvious 

 reasons. In the Batrachia, for example, such 

 as the Frog and the Toad, the ribs are 

 altogether wanting, and the strength of the 

 shoulder must consequently be provided for in 

 a peculiar manner. The scapula are enormously 

 developed so as to perform, to a certain extent, 

 the office of ribs ; and, moreover, each being 

 divided, as in Fishes, into two portions, united 

 by cartilage to each other, the strength and 

 resiliency of a chest is in some measure obtained. 

 It is, however, in the Chelonian Reptiles that 

 the most extraordinary deviation from the usual 

 arrangement is witnessed, where the scapulae 

 are absolutely placed in the interior of the 

 thorax, where they are connected by one extre- 

 tremity to the sides of the bodies of the dorsal 

 vertebrae. 



No spine or acromial process exists in the 

 scapulas of the oviparous Vertebrata, and even 

 in tho quadrupedal Mammals these parts of the 

 bone are very imperfectly developed when com- 

 pared with their condition in Man, in whom 

 alone they assume their full importance. 



The clavicle forms the second element em- 



