468 



JLLEMENTAR Y ANA TOA1Y. 



[LESS. 



pieces of various sizes. The ultimate twigs are entirely mem- 

 branous. The mucous lining of the tubes lines the ultimate 

 air-cells themselves. 



FIG. 395. BACK VIEW OF THE NECK AND THORAX OF A HUMAN SUBJECT 



from which the vertebral column and whole posterior wall of the Chest are 



supposed to be removed. 

 M, mouth; Gl, glottis; Tr, trachea; LL, left lung; RL, right lung; Br, 



bronchus; PA, pulmonary artery; PV, pulmonary veins; Ao, aorta; D t 



diaphragm ; ff, heart ; VCI, vena cava inferior. 



5. In that he has a trachea, man agrees with all Mam- 

 mals and Sauropsidans, and with the Ophiomorpha, Meno- 

 fioma, and Siren, amongst Batrachians. A trachea may, 

 however, be entirely wanting, the lungs springing immediately 

 from the larynx, as in the common Frog and Toad. It may 

 be present, but short and wholly membranous, as in 

 Salamandra. 



It may be much shorter relatively than in man in his own 

 class (as e.g. in Whales), or it may be much longer, as in 

 Ruminants. In Birds, however, it attains its maximum of 

 relative length. 



In so far as the trachea of man is a straight tube, it agrees 

 with that of all other members of his class, except the Three- 



