111 RELATIONSHIP TO REPTILES 39 
Quaternary. Some of_these were of gigantic size, 
larger even than the Ostrich. Like Archzopteryx, 
they had teeth. In Hesperornis, to take one example, 
these are very reptilian, in the way they are set in a 
long hollow in the jaw, in the absence of root and of 
cement on the neck of the tooth, in the way they 
were changed, a young tooth being formed on the 
inner side of the base of the old one. But by this 
time birds had lost their great length of tail. 
Here it will be instructive to mention the discovery 
in existing birds of what were supposed to be the 
rudiments of teeth. If you take the beak of a Parrot 
and macerate it well, you can separate the horny beak 
from the bone beneath. The horn is only a form of 
epidermis and, therefore, we should expect to find 
skin underneath. Skin is found and on it papille, 
small pimple-like elevations, similar to those found 
beneath a horse’s hoof. They nourish the growing 
and quickly wasting beak. And these were the 
“rudimentary teeth” which so much interested the 
zoological world. But here, as often, a false theory by 
stimulating investigation has led the way to the true 
one.! 
There are some very remarkable points of agreement 
between crocodiles and birds. The ordinary reptile 
has only three chambers to his heart. The crocodile’s 
heart, though still a very imperfect organ, has four 
see p. 284). He has a gizzard and_ habitually 
swallows stones to aid in digestion. His lungs are 
far more elaborate structures than those of a lizard. 
1 See Bronn’s a hiter- Reich, vol. “ Aves,” p. 501. 
