492 ZOOLOGY. 
True lips now, as in birds, border the jaw-bones, while 
salivary glands for the first time in the Vertebrates appear 
in the Chelonians and lizards ; besides these there are smalier 
glands in the lips of lizards and snakes, the poison-glands 
of the rattlesnake, viper, etc., being modifications of these 
labial glands. 
While the cesophagus is wide and the stomach usually 
quite simple, in the crocodiles there is a muscular gizzard 
approaching that of birds, and there is a special pyloric por- 
tion in the crocodiles like that of grallatorial and swimming 
birds. The liver and pancreas have, as in birds, two or more 
excretory ducts, and a gall-bladder is always present. A 
large fat-body (Fig. 440, f) is present on each side of the 
body. 
The lungs, trachea, and larynx of reptiles are much 
simpler than in birds; in the long slender-ringed trachea 
there is an approach to that of birds, but the lungs are 
modelled on the Amphibian type; the larynx, especially in 
the Chelonians and crocodiles, is much more perfect than in 
the Amphibians. 
The organs of circulation show a decided advance in situ- 
ation over the Batrachians. The heart (Fig. 440) recedes 
farther back into the thorax. Of the two auricles the right 
and larger one receives the systemic and the left the pul- 
monary veins. In all but the crocodile the ventricle has 
a partition, the right half containing venous and the left 
arterial blood, while in the crocodiles there are two ven- 
tricles, so that the heart is four-chambered. In the lizards 
two aortic branches (a right and a left) survive. In the 
crocodiles a vessel which gives off the right aortic arch and 
the carotids arises from the left ventricle, while a left aortic 
arch and the pulmonary arteries arise from the right ven- 
tricle. In the reptiles as in birds there are two superior as 
well as one inferior vena cava. In reptiles as in lower Ver- 
tebrates there are no true lymphatic glands; an organ re- 
sembling them is present in reptiles (Fig. 440, ¢h), forming a 
small swelling situated behind the angle of the lower jaw. 
While the brain is still simple, though it fills the cavity of 
the skull, the different lobes being subequal in size, the cere- 
