x-iii.] THE FROG. 197 



which lies at the sides of the back of the oral 

 cavity. The fleshy tongue will be seen, with its 

 bifurcated free end turned backwards. Turn it 

 forwards to see the attachment of its base to the 

 floor of the mouth and to the front part of the 

 lower jaw. Notice the slit of the glottis in the 

 hinder part of the floor of the mouth, and above 

 this the opening of the oesophagus. Pass a 

 bristle into the former, and a probe into the 

 latter. Notice the fine teeth in the upper jaw 

 and on the palate. 



b. The trunk. 



Tapering towards the hinder end ; and allowing 

 the hard parts of the skeleton to be felt beneath 

 the soft integument on the dorsal side, and in 

 the anterior half of the ventral aspect ; rounded 

 and soft on the greater part of the sides and 

 belly; the doacal aperture near the dorsal surface 

 of the posterior end of the trunk. 



c. The limbs. 



a. The anterior pair ; their three subdivisions, 

 brachium, antebrachium, and man us ; the four 

 digits. 



/?. The posterior pair; their length as compared 

 with that of the anterior; their subdivision 

 into femur, crus, and/^.- the five long digits : 

 the well-developed web ; the horny prominence 

 (see p. 161). 



3. Raise the integument of the abdomen with forceps 

 and slit it open with scissors from the lower jaw to 

 the origin of the hind limbs, a little on one side of 

 the middle line. Observe the spacious lymph cavities 



