396 



ORGANS OF DIGESTION 



large right (v,} and left (w) 

 lobes of the liver, passes 

 to the left side, to terminate 

 in the stomach (b,) which 

 is here as transverse in its 

 position as in the mamma- 

 lia. The convolutions of 

 the small intestine (c,) and 

 the wide colon are seen 

 between the developed 

 ovaries (y. y,) and exterior 

 to these, on each side, are 

 the long and wide oviducts 

 (1. 1. 4. 4.) with their ex- 

 panded infundibuliform 

 openings (z. z.) The rectum, (d,) as in higher vertebrata, 

 descends to the cloaca, behind the ends of the oviducts (1.1.) 

 and behind the large urinary bladder (#,) with its short ure- 

 thra, and the cloaca receives also the openings of the two 

 lateral sacs (2. 3.) before terminating in the transverse anal 

 orifice, (e^) below the base of the tail. The alimentary canal 

 has thus already acquired in the reptiles nearly all the divi- 

 sions and typical characters which it presents in the highest 

 of the vertebrated animals. 



XXII. Aves. The alimentary apparatus of birds is 

 adapted for the digestion of the higher forms of animal and 

 vegetable matter, which their locomotive and prehensile or- 

 gans enable them to obtain in the air, in the waters, and in 

 the earth. The jaws have their alveolar margins covered, 

 like those of chelonia, with horny plates, which vary in their 

 forms, according to the kind of food, like the teeth of mam- 

 malia. The nearest approach to the teeth of quadrupeds is 

 seen in the thin horny laminae disposed along the sides of 

 the bills in the mallard, and some other aquatic birds ; and in 

 the earliest condition of the birds the laminae begin by a 

 series of small detached tubercles, provided each with 

 its pulp, its nerve, and its vessels, like the horny maxillary 

 plates of the whale, and the more solid calcareous teeth of 



