590 _ AMPHIBIA. 
pro-otics. Connecting the fenestra ovalis of the ear with 
the tympanic membrane, which is flush with the skin, there 
is a delicate bony rod—the columella. This lies in the 
Eustachian tube, which opens into the mouth at the corner 
of the gape. 
The nostrils open into small nasal cavities, with folded 
walls of sensitive membrane; the posterior nares open into 
the front of the mouth. 
There are taste papilla on the tongue, and touch-spots 
on the skin. 
Alimentary system.—The frog feeds in great part on 
insects, which it catches dexterously with its tongue. This 
is fixed in front and loose behind. There are teeth on the 
premaxille, maxilla, and vomers. Into the cavity of the 
mouth the nasal sacs open anteriorly, and the Eustachian 
tubes posteriorly. The males of Rana esculenta have a pair 
of resonating sacs which open into the mouth cavity at the 
angle of the jaw, and are dilated during croaking. The 
tongue bears numerous taste papille. Behind the tongue 
on the floor of the mouth is the glottis, the opening of the 
short larynx which leads to the lungs. The larynx is sup- 
ported by two arytenoid cartilages, and also by a ring; with 
the arytenoids the vocal cords are closely associated. The 
lungs lie so near the mouth that laryngeal, tracheal, and 
bronchial regions are hardly distinguishable. On the floor 
of the mouth is the hyoid cartilage, which serves for the 
insertion of muscles to tongue, etc. 
Of the (4) gill-clefts which are borne on the walls of the 
pharynx in the tadpole, there are no distinct traces in the 
adult. The lungs develop as outgrowths from the gullet. 
The gullet leads into a tubular stomach, which is not 
sharply separated from it. There is a pyloric constriction 
dividing the stomach from the duodenum, or first part of 
the small intestine. After several coils the small intestine 
opens into the wider large intestine or rectum, which enters 
the cloaca. 
The liver has a right and a left lobe, the latter again sub- 
divided. ‘The gall-bladder lies between the right and left 
lobes; bile flows into it from the liver by a number of 
hepatic ducts, which are continued onwards to the duodenum 
ina common bile-duct. The pancreas lies in the mesentery 
