REPTILIA. 



Fig. 333. 



Skeleton of the Frog. 



but all the bones of the spine have become consolidated into ten ver- 

 tebrae, firmly connected together by strong articulations, while the flexible 

 tail of the tadpole has 

 become converted into a 

 strong and immoveable 

 os coccygis, composed of 

 a single piece. 



(1901.) No ribs what- 

 ever are met with in the 

 Frog; and even in those 

 Amphibia which are 

 possessed of these ele- 

 ments of the skeleton, 

 they are mere rudi- 

 ments appended to the 

 extremities of the trans- 

 verse processes of the 

 vertebrae. The sternum, 

 however, is largely de- 

 veloped, and gives extensive attachment to the muscles of the abdomen. 

 The anterior extremities are supported by a semicartilaginous zone, in 

 which the three elements of the shoulder (the scapula, the clavicle, and 

 the coracoid bone) are distinctly recognizable ; and the bones of the arm, 

 fore-arm, and hand are very perfectly formed. 



(1902.) The pelvis is large and firmly ossified, in correspondence with 

 the strength and magnitude of the hinder extremity, the ossa ilii being 

 articulated to the ends of the transverse processes of the last vertebra, 

 which from this circumstance maybe called the sacrum. The tibia and 

 fibula are consolidated into one bone ; while two of the bones of the 

 tarsus (the astragalus and the os calcis) are so excessively elongated 

 that they might almost be taken for a second tibia and fibula, did not 

 their position indicate their real nature. 



(1903.) One circumstance is remarkable in the construction of the 

 shoulder-joint of these reptiles, which are found to have a strong liga- 

 ment passing between the head of the humerus and the scapula, exactly 

 in the same manner as the ligamentum teres of the human hip-joint. The 

 use of such a deviation from the ordinary structure of the articulation is 

 obvious : the Frog, as it alights from those long and vigorous leaps which 

 form its ordinary mode of progression, receives the whole shock of its 

 fall upon its fore-legs, and thus this ligament becomes needful as an 

 additional security to the articulation in question. 



(1904.) The skeleton of an Ophidian Reptile presents a strange con- 

 trast to that of the Batrachian, last described. Taking the Boa Con- 

 strictor as an example of this order, we find the spine of this enormous 

 serpent composed of three hundred and four distinct vertebrae, of which 



