94 Elementary Manual of Zoology. 
(2) Females, without these vocal sacs. 
In the head make out the following parts :— 
(1) The large wide mouth in front. 
(2) The two large eyes situated above the head. Notice the 
semi-transparent lower eyelid with whieh the eye can be 
covered up. 
(3) The twocnostrils situated between the eyes and the end of thé 
mouth. 
(4) The circular smooth tympanic membrane on either side of 
the head behind the eye. 
Open the mouth as wide as you can, and cut down on either side a 
short way with your scissors, to still further increase the gape. Make 
out the following :— 
(1) The large soft bifid ‘tongue, which occupies the floor of the 
mouth. It is attached in front and free behind. , 
(2) The wide esophagus, into which the mouth passes behind. 
(3) The slit of the glottis, through which air passes down into 
the lungs. It lies in the middle line behind the tongue. 
(4) The two posterior nasal openings in the roof of the mouth. 
They are connected with the nostrils in front, 
(5) The openings of the large eustachian recesses, which lie on 
either side at the back of the roof of the mouth. Each 
communicates with the cavity behind the tympanic 
membrane. 
(6) The minute teeth with which the upper jaw and roof of the 
mouth are armed. 
Examine the fore-limb and make out—the basal joint or branchium, 
which is supported by the humerus bone; the second joint or forearm, 
supported by the fused radius and ulna; and the hand, consisting of four 
digits, corresponding to the four fingers in man, the thumb being 
rudimentary. 
Examine the hind limb and make out ; the basal joint (femur), which 
is supported by the femoral bone; the leg, which is supported by the 
fused tibia and fibula ; the tarsal joint, supported by two elongated tarsal 
bones ; and the five digits, which are connected together by webbed 
membrane. 
Lay the animal on its back on the weighted bark and pinit down 
firmly, inserting the pins in the muscles of the fore and hind limbs, 
Slit open the skin down the middle line from the lower jaw to the 
hind legs, noticing the large ‘spaces which lie between the skin and the 
muscles. Jin back the flap of skin on either side, so as to expose the 
muscular wall of the abdomen. Notice the large (muscular cutaneous) 
vein which is usually visible on either side ; this is a branch of the sub- 
elavian vein, which we shall come to later. 
