18 GENERAL ANATOMY OF THE FROG 



is soft and fleshy, but is slightly stiffened by a car- 

 tilaginous plate — the body of the hyoid. 



b. The tongue, which is thin and fleshy, is attached to 



the front part of the floor of the mouth, and has its 

 free bilobed end turned backwards towards the throat. 

 Turn the tongue forwards with the forceps. 



c. The glottis, or aperture of the larynx, is a longitudinal 



slit in the floor of the posterior part of the mouth, 

 and is stiff'ened laterally by the arytenoid cartilages. 



Pass bristles through ilie glottis into the lungs. If 

 amy difficulty is experienced in fmding the glottis 

 snip through the amgles of the mouth with scissors, 

 so as to allow the mouth to be opened more widely. 



C. The Abdominal Viscera. 



Lay the frog on its bach under water, amd fasten it down to 

 the dissecting board by pins through the limbs. Cut through the 

 skin, along the middle line, the whole length of the ventral sur- 

 face. Separate the skin from the underlying parts, noticing its 

 very loose attachment to these parts, and the large space — a lymph 

 cavity — beneath it. Turn the flaps of skin outwards, and pin 

 them, back. Notice : 



a. The muscles of the body- wall. 



b. The pectoral or shoulder girdle : a bony arch running 



across the body, opposite the fore hmbs. 



Pinch up unth forceps the muscular body-wall, and cut through 

 it into the body-cavity or ccelom with scissors a little to one side 

 of the median line, being careful not to injure the anterim' abdo- 

 minal vein which runs along the inner surface of the body wall 

 in the middle line. 



Continue the cut backwards to the hinder end of the body, and 

 forwards to the jaw, cutting through the pectoral girdle vnth strong 

 scissors, and taking care not to injure the pa/rts beneath. 



Note on the inner surface of the larger flap the anterior abdo- 

 minal vein, and carefully dissect this from the flap. Pull the two 

 flaps apart, cutting through them transversely at their posterior 

 ends to facilitate tfie process, and turn them back so as to display 

 the viscera. 



