RANA. 341 
rectum which opens into the cloaca. From its ventral wall, 
close to the cloacal aperture, is a large bilobed w7znary 
bladder. 
Close to the pancreas, and near the head of the rectum, 
is a round reddish sf/een, one of the ductless glands.. 
At the extreme front end of the abdominal ‘cavity there 
lies dorsally a pair of Zzmgs. Each rests loosely in the cavity, 
but is attached anteriorly to the cesophagus. 
If the lungs be inflated by a blowpipe through 
the glottis they will be seen to consist of hollow sacs of 
great elasticity. When punctured they return to their former 
small bulk and soft condition. 
Respiratory. 
Fig. 240.—DIAGRAM OF VENOUS SYSTEM OF A FROG. 
(Ventral view.) 
External Jugular. 
Lingual, Sinus Venosus, 
Mandibular. | | Precaval. 
Internal Jugular. q \y : 
* Subscapular. Subclavian. 
Innominate. 
Musculo- 
cutaneous. 
Portal. 
Gastric, 
Mesenteric. 
Branches. 
Pelvic. Renal Portal. 
Renal Portal. 
Sciatic. 
Femoral. 
, 6 
The anterior abdominal is unlabelled, but is seen running forwards from the 
two pelvics to the portal. 
The frog fills its buccal cavity with air through the nares, 
and then pushes upwards the floor of the cavity with its 
hyoid cartilage (or lingual plate). This forces the air down 
to the lungs and effects izspiration. The-air is expired by 
the elastic walls of the lungs.* We may notice. that the 
* The expiration may be assisted by contraction of the abdominal muscles upon 
the viscera. 
