26 CROCODILES. 



Although these creatures are capable of walking upon land, for which purpose they 

 are furnished with four legs, they are more fitted for the water than its shores, and are 

 swift and graceful in the one, as they are stiff, awkward and clumsy on the other. 

 Through the water they urge their course with extraordinary speed, their long, flat- 

 tened, flexible tail answering the double purpose of an oar and a rudder, but on land 

 their bodies are so heavy and their legs are so weak, that they can hardly be said to 

 walk, a term which seems to imply that the body is wholly supported by the legs, but 

 to push or drag themselves along the ground, on which rests a considerable portion of 

 their weight. 



The head of these creatures is always rather elongated, and in some species is 

 lengthened into a narrow and prolonged snout. Each jaw is furnished with a row of 

 sharply pointed and rather conical teeth. These teeth are hollow, mostly grooved on 

 the surface, and are replaced when they fall by new teeth that grow behind them, and 

 in process of time push the old ones out of their sockets. 



The nostrils are placed at the very extremity of the skull and upon a slightly raised 

 prominence, so that the animal is able to breathe by merely exposing an inch or so 

 above the water, and thus can conceal itself from almost any foe, or make an unsus- 

 pected approach upon its prey. There is yet another more important use for the 

 position of the nostrils. The Crocodiles feed on fishes and various water-loving creat- 

 ures, but also are in the habit of lurking by the river-bank, and suddenly seizing upon 

 any unfortunate animal that may come to drink. Suppose, for example, that a calf or 

 a dog is thus dragged into the water, the reptile grasps it across the body, and sinks 

 below the surface so as to keep the head of the victim below water while itself can 

 breathe by means of the elevated nostrils. 



But as during this process the mouth is held widely open, it might be rationally pre- 

 sumed that considerable inconvenience would be caused by the water running down 

 the throat. Such would indeed be the case, were not this difficulty provided for by a 

 simple yet very wonderful contrivance. At the back of the throat, a pair of thin car- 

 tilaginous plates are so arranged, that when the animal opens its mouth the pressure 

 of the water rushing into the mouth immediately closes one upon the other, and effect- 

 ually prevents the passage of a single drop, the closure being in exact proportion to 

 the volume of water. The structure indeed is very like that of the valves of the heart. 

 The channels which lead from the nostrils run very far back through the skull, and 

 open behind the throat valves, so that respiration is in no way impeded. They can- 

 not, however, swallow their prey while under water, but are obliged to bring it on shore 

 for that purpose. The tongue is small, and fastened down to the lower jaw throughout 

 its length, so that it was formerly thought that the Crocodiles were destitute of that organ. 



There is rather a curious structure in the vertebras of the neck. These bones are 

 furnished with short transverse processes like false ribs, which have the effect of pre- 

 venting the animal from turning its head from side to side. On land, therefore, where 

 its feeble limbs are so inadequate to the support of the long and heavy body, it can 

 easily be avoided by any one of ordinary agility. The eyes are large, and set rather 

 far back upon the head. The ears are carefully guarded from the ingress of water by 

 a pair of tightly closing valves. Below the throat are a pair of glands which secrete a 

 substance having a strong musky scent which is very disagreeable, and in old individ- 

 uals taint the whole flesh with its rank odor and render it uneatable to ordinary palates. 



The young of these reptiles are hatched from eggs, which are strangely small in pro- 

 portion to the large dimensions of the adult animal, the newly hatched offspring being 

 so small as hardly to be recognized as belonging to the same species as their parents, 

 especially as there are certain differences of shape, hereafter to be mentioned. 



These great reptiles are divided, or rather fall naturally, into two families, namely, the 

 Crocodiles and the Alligators. All the members of these families can be easily distin- 

 guished by the shape of their jaws and teeth, the lower canine teeth of the Crocodiles 

 fitting into a notch in the edge of the upper jaw, and those of the Alligators fitting into 

 a/// in the upper jaw. This peculiarity causes an obvious difference in the outline of 

 the head, the muzzle of the Crocodiles being narrowed behind the nostrils, while that of 

 the Alligators forms an unbroken line to the extremity. A glance therefore at the head 





