ANATOMY OF THE CROCODILE. 263 



striking ; and it will be found that the pits in the pre-maxillary bones, for the reception of the tops of the 

 lower incisors, are sometimes perforations. The teeth are all sharp, conical, and tapering where visible, 

 but they have a hollow cylindrical fang, which is set in a special hole or alveolus in the jaw. Crocodiles 

 snap and tear, and thus wear or drag out their teeth, and they are constantly replaced by larger ones, for 

 the creature's first teeth bear but a small relation in size to those of old age. Each tooth is hollowed 

 out at the fang, so as to serve for the case or sheath of the genii of the tooth destined to replace it, 

 which is to be larger. The sockets for the teeth are surrounded by the bone of the pre-rnaxillary and 

 maxillary bones of the upper and deiitary bones of the lower jaw, and are fixed in 

 so as to be very strong, and a fleshy cover extends around their starting-point from 

 the jaw. As the animal grows old, the size of the teeth is not the same in all parts 

 of the jaws. 



Seizing its prey, the Crocodile, if there is any struggle, drowns it, and can 

 manage to do so with its jaws stretched out grasping its prey, for it has a special 

 structural arrangement by which the water is prevented from rushing down its own 

 throat and producing suffocation. First of all, before noticing this, it must be stated 

 that, unlike the Chelonian reptiles, the Crocodilia can breathe with the mouth open, 

 and that the air rushes into their lungs when their movable ribs expand ; for although 

 the skin is tough and armour-plated, it is not supported by a bony expansion which 

 restricts the movements of the ribs. They have a more or less rudimentary, but still 

 very useful, diaphragm. 



The nostrils of the Crocodilia, situated near the end of the snout, are capable of 

 being closed at the will of the animal, and they are connected in the snout with a 

 passage, which is limited below, not as in the Mammalia, by palate-bones alone, 

 but also by pterygoids, and which opens far back in the throat. The roof of the mouth 

 has a membrane on it that ends backwards in a fold which, taking away the uvula, 

 resembles that of man in position. This upper fold rests on the back of the tongue 

 when the mouth is closed, and the air passes above and behind it into the throat be- 



GR.O ii\ Til OF TOOTH 



fore reaching the lungs. The tongue is a large flabby structure, incapable of pro- OF CROCODILE. 

 trusion, and has a hyoid bone at its broad hinder part in the throat, and on it and the (< \ ) : el ^ ( i l ! ( j" U T otu 

 tongue is a lower Map of membrane reaching across the throat, and parallel at its 



of third Tooth which 



free edge with the upper fold. When the Crocodile drags a struggling animal in due time win 



, , 6 . ., . . ., , ., , ., . , , , f ", , , ceed and displace 6. 



into the water m its jaw-grip, it shuts its nostrils, sinks down, and closes the back 

 of its throat by muscular action, which brings the upper and lower membrane folds together. No 

 water can then pass into the throat. After a while the Crocodile just raises the tip of its snout above 

 water, opens the valves of its nostrils and takes in air, which passes along the passage above the palate, 

 behind the folds of skin into the throat, and thence into the lungs. It tears its prey, if soft ; should it 

 not be able to bolt it, it hides it away until decomposition softens the tissues and permits them to be 

 swallowed. The food passes along a narrow long gullet and oesophagus to a single globular stomach, the 

 mucous membrane of the passage being folded and villous, but that of the stomach is very thin. The 

 opening in the stomach for the intestine is close to that for the oesophagus, and there is a small pyloric 

 cul-de-sac separated off from the main cavity, through which food must pass into the intestine. The 

 stomach has the mucous membrane thin, and it is folded and placed in serpentine ridges : the cellular 

 coat outside it is thick, and the more external muscular tunic, made up of fibres radiating from the 

 centre to the circumference, issuing from a kind of disc of membrane, is very strong. This stomach i.s 

 not without its resemblance to the gizzard of a Heron. The food gets crushed and digested in part 

 there, and passes into a much-folded small intestine, with a peculiar glandular layer, and then into a 

 large gut with internal projections on its membrane. 



The organs of special sense are elaborate in the Crocodilia. Thus the eye may have a vertical 

 or a horizontal pupil, according to the nocturnal or crepuscular habits of the species, and all have the 

 ciliary processes fully and beautifully developed. A peculiar vascular membrane, covered with pigment, 

 projects into the vitreous humour of the globe, and then is connected with the capsule of the lens. 

 The upper and lower eyelids are well developed. There is a transparent nictitating membrane 

 moved by a special muscular apparatus, and there is a gland especially destined to facilitate the move- 



