106 



LEAVES FROM THE NOTE-BOOK OF A NATURALIST. 



some fleshy fibres adhering to that part of the per- 

 itoneum which covers the liver, remind the ob- 

 server of a diaphragm. This organization, com- 

 bined with their trilocular heart, where the blood 

 coming from the lungs is not mingled with the 

 venous portion of that fluid, which comes from 

 the body, so completely as it is in other reptiles, 

 approximates, though in no great degree, the croc- 

 odilians to the warm-blooded quadrupeds. As 

 in the tortoises, the auditory bone and the ptery- 

 goid apophyses are fixed to the skull. 



But the jaws, which in the chelonians are 

 edentulous, are furnished with numerous large 

 conical teeth of unequal length, implanted in a 

 single row in the thickness of the upper and low- 

 er maxillary bones, in separate cavities, each of 

 which may be looked upon as a true alveolus or 

 socket. This formidable array is constantly kept 

 up in good order and condition by a provision 

 which insures a constant supply of serviceable 

 teeth. Each tooth is hollowed at the base, so as 

 to become the case or sheath of the tooth of 

 greater size destined to replace it ; so that, in the 

 crocodiles, the operation of teething is always 

 painlessly going on : nor does the number of the 

 teeth vary according to age. The pressure of the 

 rising tooth causes an absorption of the hollow base 

 of the old one ; and as the former advances the 

 latter dwindles, till it drops out and is succeeded 

 by the new one. It need hardly be observed 

 that great solidity and strength result from this 

 double gomphosis ; while, to add to the firmness 

 of the terrible apparatus, the sockets are directed 

 obliquely from front to rear. Each tooth is, so 

 to speak, insulated ; and a gum, or at least what 

 does duty for a gum, covers the bony edges of 

 the jaws whence they spring. 



The depressed and elongated body and tail are 

 shielded on the back by solid carinated scutch- 

 eons. The scales of the belly are squared, com- 

 paratively delicate, and smooth. The tail is long- 

 er than the body, compressed laterally, and its 

 scales are elevated into a central ridge. The 

 fore-feet are furnished with five toes, the hind-feet 

 with four. All the toes are armed with claws, 

 and more or less webbed. The nostrils open at 

 the end of the muzzle, and are raised and fur- 

 nished with crescent-shaped slits. This elevation 

 is very strongly marked in the Gavials or Gharri- 

 als, and enables the animal to lie floating with the 

 nostrils above the water without exposing much 

 of the head. They are closed by valves when 

 the creature descends. The fleshy flat tongue is 

 attached very nearly up to the edges ; whence the 

 notion of the ancients that the crocodile had none. 

 This conformation prevents, in a great measure, 

 the routing out of leeches, &c., by muscular ac- 

 tion, and accounts for the necessity of external aid 

 in freeing the mouth from annoying parasites. 

 The lower jaw is prolonged backwards beyond the 

 skull, and the gape is proportionably elongated. 

 Hence, when the animal raises its head and 

 throws it a little backwards on opening the mouth 

 by the depression of the lower jaw, it has the ap- 



pearance of moving its upper jaw, whence the 

 error of the ancients in that respect. 



Cuvier observes that the crocodiles cannot swal- 

 low when in the water, but the evidence of those 

 who have seen alligators in their fishing expedi- 

 tions hardly supports this assertion. It is true 

 that such witnesses relate, that, after having seized 

 the fish beneath the surface, the captor rises above 

 it, and occasionally tosses the prey into the air. 

 as if to get rid of the water taken in at the 

 time of the seizure ; but there can be no question 

 that, on such occasions, the fish is swallowed by 

 the alligator without leaving the water ; though 

 the latter repairs to the land for the purpose of 

 deveuring such land animals as it may have 

 succeeded in surprising and drowning, after they 

 have undergone such a degree of decomposition as 

 renders their fibre tender and more easily divided 

 by crocodilian teeth. With all due submission, 

 then, to the high authority of the great French 

 zoologist, his position may be doubted ; and, in- 

 deed, the careful adaptation of a part of its organ- 

 ization to the requirements of the animal goes far to 

 contradict it. This conformation we shall endeav- 

 or to explain with as little technicality as possible. 

 If the interior of the mouth of a crocodile 01 

 alligator be examined, the roof of the palate will 

 be found nearly flat, and not pierced by the 

 extremities of the nasal fossa, as in the greater 

 number of other reptiles. No ; the posterior na- 

 sal apertures open in the pharynx behind the pala- 

 tine veil, which is sufficiently elongated to over- 

 spread that portion of the roof which is in front 

 of the glottis, or opening of the windpipe. Indeed, 

 it is probable that the crocodiles are the only rep- 

 tiles that have a true pharynx, in other words, a 

 vestibule common to the mouth, the posterior nos- 

 trils, the larynx or windpipe, and the oesophagus 

 or gullet. This arrangement of the parts in com- 

 bination with the muscular structure of the tongue, 

 the bone of which, or os hyoides, has a peculiar 

 expansion, produces a sort of disk or valve, which 

 can be lifted and applied to the velum palati above, 

 so as effectually to protect the glottis and perform 

 the office of the epiglottis in mammiferous animals, 

 conferring on the crocodile a peculiar power of 

 deglutition and respiration when it has seized its 

 prey below the surface of the water, or has 

 dragged it down from the land. The same admi- 

 rable machinery comes also into play in carrying 

 on respiration, when the animal lies with its 

 muzzle alone above the surface of the water. 



The eggs of the crocodile are covered v.ith a 

 hard shell, and are as large as those of a goose, 

 but not so oval. The female is said to guard the 

 nest or place of deposit, and to bestow maternal 

 care upon the young during some months. 



The form is widely spread. Asia, Africa, and 

 America, have it. There is no authentic record 

 of its ever having inhabited Europe, in the present 

 state of the world at least ; unless we are to give 

 credit to the assertion of Malte-Brun, that one 

 was taken in the Rhone some two centuries ago. 

 The fifth quarter of the globe, Australasia, has not 



