CEOCODILUS NILOTJCUS. 19 
assailed by a swarm of gnats. He experimented with a dead crocodile, and he says its 
mouth was not so hermetically closed that gnats could not find an entrance, and 
consequently he discovered the palate of this dead animal covered with a brownish- 
black crust, made up of a multitude of gnats, ranged side by side, with their trunks 
buried in the ducts of the glands that abound in the mouth of the crocodile. He 
believed the same happened in the case of a living crocodile basking with its mouth 
open on a sandbank, but whether this really does occur he had no means of testing by 
actual observation. Nevertheless he accepted it as an established fact, and adds : — 
" II est certain que si, dans l'etat d'imperfection de ses organes, le crocodile eut ete, au 
grand jour de la creation, reduit a ses seuls moyens, c'est a dire qu'il eut ete delaisse 
sans autre ressource, cette espece n'aurait pu traverser les siecles et arriver a nous.'' 
The imperfections of structure to which he referred were the seeming inability of the 
crocodile to free its palate from gnats by the use of its fore limbs and the nearly 
immobile character of its tongue. He did not accept Aristotle's statement that the 
trochilus entered the crocodile's mouth to clean its teeth, as he thought that the animal 
itself could perform this part of its toilet with its hind feet. The difficulty of a 
crocodile freeing its mouth from insects, should they enter and settle on it, seems purely 
imaginary, as the mere closure of the mouth would at once suffice, not only to exclude 
them, but also to destroy them effectually. 
The habit of lying with the mouth open is not confined to large crocodiles, as the 
young do the same ; but as all the birds hitherto regarded as the crocodile bird are of 
such dimensions that they could not enter the mouth even of a specimen one-third 
grown, far less that of the young, the question naturally arises, if the trochilus is so 
essential to the existence of the crocodile, how are the mouths of these young 
specimens freed of their mortal foes X 
Everyone acquainted with Egypt knows how the domestic animals in the fields and 
on the banks of the river are pestered by the attacks of insects, and how birds are 
drawn towards them in quest of their insect prey, and tolerated by the cattle, asses, 
and camels owing to the relief they afford. It is the same with the crocodile and 
the hippopotamus. 
The crocodile, however, from the nature of its food, is the host of many parasitic 
worms 1 , which, while the animal lies basking in the sun, find their way into its mouth, 
doubtless brought up by the stimulating action of the air on the pharynx, and refiexly 
on the oesophagus and stomach. The presence of these worms would also prove an 
attraction to some birds, and it was doubtless to them that Macoudi 2 referred when he 
said that whatever the crocodile eats turns into worms in its belly ; and he added that 
the crocodile, whenever it felt itself inconvenienced by them, came out of the water on 
1 Mr. "Wenharu (Gould's ' Birds of Asia,' vii., art. Pluvianus cegyptius, April 1865), who dissected a Nile 
crocodile 14 feet long, could not find any parasites, but they are known, to exist all the same. 
2 Les Prairies d'Or (Trans. Soc. As. Paris, 1861-74), i. p. 235. 
D2 
