XXIIl] 



LACERTA VIVIPARA 



579 



the central cavity is easily recognised as a wide space : whilst in 

 Crocodiles and Tortoises, still more so in Birds and Mammals, it is 

 represented only by the bronchial tubes. 



The lungs are connected with the glottis by a comparatively 

 long stalk, the trachea or windpipe, which is stiffened by rings of 

 cartilage. A similar structure is 

 found amongst Amphibia in the 

 Gymnophiona and in a few Uro- 

 dela. Immediately below the glottis 

 the trachea is enlarged. The 

 enlarged portion is stiffened by a 

 large, broad, ring-shaped cartilage, 

 the cricoid, to which are arti- 

 culated twoarytenoid cartilages. 

 The whole structure consisting 

 of the dilatation of the trachea 

 and its cartilages is called the 

 larynx. 



The lizard like the Frog lives 

 principally on insects and is pro- 

 vided with a long mobile tongue 

 cleft at the tip, by means of which 

 the prey are whisked into the 

 mouth. The tongue is free in 

 front and attached behind, so that 

 in the lizard there is the opposite 

 arrangement to what is found in 

 the Frog. The teeth are simple 

 and conical, and are implanted in 

 a groove on the inner side of the 

 bones bearing them. As the lizard 

 grows they become actually fused 

 with the bone along the side of 

 the groove and as they are worn 

 out they are replaced by others de- 

 veloped from the groove. 



13 



13 



FIG. 286. Diagram to show arrange- 

 ment of the principal veins in the 

 Anura and Eeptilia. 



1. Sinus venosus, gradually disap- 

 pearing in the higher forms. 

 2. Ductus Cuvieri = superior vena 

 cava. 3. Internal jugular = anterior 

 cardinal sinus. 4. External jugular 

 = sub-branchial. 5. Subclavian. 

 6. Posterior cardinal, front part 

 = vena azygos. 7. Inferior 



vena cava. 8. Renal portal = 

 hinder part of posterior cardinal. 

 9. Caudal. 10. Sciatic = internal 

 iliac. 11. Pelvic. 12. Anterior 

 abdominal. 13. Femoral = 



external iliac. 



When a Frog's mouth is forced 

 open, amongst the most striking features of the roof of the mouth 

 are the two large eyelfells shining through. When we open the 

 mouth of a lizard nothing of the eyes can be seen. There is pro- 

 jecting inwards from the upper lip on each side a flap, the palatal 



372 



