THE LIZARD. 175 



the left being ventral to that of the right : all three arterial 

 apertures lie to the left of the auriculo-ventricular aperture. 



XXIV. By the removal of the heart, the lungs are 

 thoroughly exposed ; note in them the following 

 points : 



213. Each lung is a fusiform sac, very thin in its posterior 

 half, much thicker anteriorly : on cutting it open, the wall 

 is seen to be raised into a network of delicate ridges, pro- 

 ducing a honey-combed appearance : the network is closer 

 and the ridges more marked at the anterior than at the 

 posterior end of the lung. 



214. The bifurcation of the trachea into two very short 

 tubes, the bronchi, which communicates each with the 

 corresponding lung by a small aperture a short distance 

 from its apiculate anterior end. 



215. The complete cartilaginous rings of the trachea and 

 bronchi. 



XXV. Slit up what remains of the gullet along one 

 side, and continue the incision forwards, through 



O 



the floor of the mouth, close alongside the inner 

 edge of the mandible ; turn aside the floor of the 

 mouth so as to expose the oral cavity : if the 

 latter is not sufficiently displayed, part of the 

 mandible may be cut away with bone forceps. 

 Observe 



216. The tongue, a narrow, elongated, fleshy organ on 

 the floor of the mouth, bifid in front. 



217. The glottis, or aperture of the trachea into the 

 mouth, a small longitudinal slit, placed at the summit of a 

 rounded prominence in which are contained the -cartilages 

 of the larynx. 



218. The small, conical teeth, arranged in a single series 

 round the upper and lower jaws (premaxillary, maxillary, 



