REPTILE. 



547 



r This fact of being intermediate in their motions and 

 also in their principal localities, very naturally loads 

 to the conclusion, that they are also intermediate in 

 their history; that, for example, in respect of any par- 

 ticular place on the surface of the earth, they stand 

 intermediate between the times when the principal 

 character of that place is water, and when it is land. 

 We are generally disposed to regard the ancient 

 account of the Ultima Tliule, which was placed in the 

 extreme north, as a mere fable ; but really nee tell us 

 iicc mare is the very kind of country which would 

 suit the great saurian reptiles which are found in the 

 earth ; and we may add, that, if the parts with which 

 the bones of some of these creatures were covered, 

 bore any proportion in singularity of structure to the 

 bones themselves, a tolerable foundation is furnished 

 for many of the monsters of antiquity, without much 

 necessity for having recourse to fable. Thus, if the 

 history were complete, which unfortunately it is not, a 

 proper knowledge of the reptiles would throw more 

 light upon the ancient history of the globe than could be 

 obtained from any other animals ; because the others 

 indicate a fixed state of things with the surface, either 

 land or water, and the reptiles indicate the transition 

 from the one of these to the other. As they exist, 

 they belong to places of great stimulus and excite- 

 ment ; and we may presume that when they were 

 more general, that state of things was more general 

 also. 



The next part of the subject will be the considera- 

 tion of the particular kind of structure which the 

 reptiles bring to the performance of their duty in 

 nature ; or, rather, the kind of structure which enables 

 them, and indeed compels them, to be so obedient to 

 the action of physical causes. In this we shall glance 

 very briefly at the different systems and structures, 

 with the way in which they act or are acted upon ; 

 and having done this, we shall give a mere outline of 

 the classification. 



In this first part the skeleton is always the portion 

 to begin with. We have remarked that in general 

 the bones contain less salt of lime than those of land 

 animals, but there are differences in this respect. 

 The bones of the small ones are of the same structure 

 throughout, without any cells for containing marrow ; 

 but in the larger Sauria there are such cells, though 

 comparatively few in number. 



The cranium properly so called.or the bony protection 

 of the brain, is very small in all reptiles, which forbids 

 our supposing that the energy is much concentrated 

 in that organ, or that the senses of which the organs 

 obtain their nerves immediately from the brain can 

 be very acute. The vast production of the jaws in 

 some of the species makes the head appear large. 

 There is very often a considerable difference between 

 the young animal and the adult in the form of the 

 head ; and one who was not aware of this would be 

 apt to set them down as different species. This is 

 the case, to a very considerable extent, with the cro- 

 codiles. When young, their foreheads are rounded 

 in the contour, their muzzles are short and blunt, and 

 the eyes are placed about the middle of the lenglh of 

 the head ; but as they increase in size, the roundness 

 ot the forehead disappears, the jaws lengthen, the 

 head appears very flat, and the eyes have a backward 

 situation, so that they are three-fourths of the total 

 length of the head from the point of the muzzle. In 

 them, and also in the tortoises, the skull is a sort of 

 flattened cone, with the brain in the posterior or basal 



part ; and in others of the order it is a prism with 

 the edges rounded ; but in all the cavity for the brain 

 is simple, and of nearly the same width throughout 

 its length. 



The vertebral column varies much in the reptile?, 

 and in some of them there is hardly any distinction 

 ot" articulated parts ; while in others there are some 

 of the most varied and perfect motions in the whole 

 mechanical structure of animals. In the tortoises, 

 crocodiles, and some others that have distinct necks, 

 the number of vertebras is seven, the same as in the 

 mammalia. The vertebrae of the back vary in dif- 

 ferent tortoises, being not more than eight in some, 

 and as many as eleven in others ; and there are gene- 

 rally three vertebra; in the tail. Those of the tail 

 have considerable motion ; and in the neck they 

 have more extent and variety than is to be met with 

 in so short an organ in any other animal ; and, besides 

 those that move the joints of the neck, there are 

 other long ones attached to the frame-work farther 

 back, by means of which the creature may be drawn into 

 the horny shell. The vertebra of the back have not 

 the slightest motion, but are soldered into one piece 

 with the bones which answer to the ribs, and the 

 shield or dorsal portion of the shell. In the crocodiles 

 there are twelve vertebrae in the back, five in the 

 loins, two answering to the sacrum, and thirty-four in 

 the tail ; but, except in the tail, the articulations have 

 not much freedom of motion. The frogs have about 

 eight or ten vertebra 1 , according to the species ; but 

 as these form a simple column without any ribs 

 attached, they cannot be distinguished like those of 

 an animal having ribs. The spinal muscles are 

 concentrated upon the neck in the tortoises, upon 

 the tail in most of the Sauria, and in the frogs they 

 are few. 



The thorax, for it cannot be called the chest in all 

 the species, varies a great deal. In the tortoises the 

 ribs are confined in the shield on the back, and the 

 sternum is blended in the breast-plate. The Sauna 

 have the anterior part of the sternum bony to admit 

 of attachment to the clavicles, but it passes into car- 

 tilage backwards, and ultimately divides into eight 

 cylindrical cartilages, which brace and strengthen the 

 belly like ropes. The ribs are twelve, but the two 

 nearest adjoining the front, and the two in the rear, are 

 not attached to the sternum. Some of the lizards 

 have the greater part of the ribs joined by cartila- 

 ginous arches ; the salamanders have them only rudi- 

 mental, and the frogs, though they have no ribs, have 

 a sternum. Thus, from the crocodiles to the frogs, 

 there is a gradual lessening of the connexion between 

 the dorsal part of the spine and the sternum. The 

 muscles which give motion to the same parts of the 

 body are not very powerful ; and in the tortoises and 

 frogs which have no motion of ribs, the abdominal 

 muscles are attached to the breast-plate and the ster- 

 num. This enables the frogs to inflate the body by 

 swelling out the skin of the sides. 



The cavity in which the head of the humerus, or 

 first bone of the anterior extremity acts is, in the 

 majority of reptiles, with feet formed in two bones 

 the blade-bone, and what is usually called the cla-, 

 vicle. It is doubtful, however, whether this clavicle, 

 which is a short flat bone extending from the sternum 

 to the shoulder-joint, is not a cnracoid bone like that 

 which supports the wing-joint of birds from the ster- 

 num ; and this is rendered the more probable bv the 

 turtles having a i'urcal bone somewhat resembling 

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