PHYLUM CHORDATA 



659 



and to the pulmonary artery. In connection with various parts of 

 the respiratory system there are cavities containing air. The 

 connection of the tympanic cavity with the pharynx by means of 

 the Eustachian tubes has been already mentioned. Air-sinuses, 

 connected with the nasal chambers, extend into the bones of the 

 A B 



r T3.ol 



I it I IjHi 



* Hup JIT f 



FIG. 1214. Brain of Dog. A, dorsal ; B, ventral ; C, lateral aspect. B. ol. olfactory bulb ; 

 Cr. ce. crura cerebri ; Fi. p. great longitudinal fissure ; HE, HE', lateral lobes of cerebellum ; 

 Eyp. hypophysis ; Med. spinal cord ; NE, medulla oblongata ; Po. pons Varolii ; VH . 

 cerebral hemispheres ; Wu, middle lobe (vermis) of cerebellum ; I XII. cerebral nerves. 

 (From Wiedersheim's Comparative Anatomy.) 



skull, especially into the maxillae and frontals, where they may 

 reach large dimensions, and are known as the maxillary antra and 

 frontal sinuses. Air-sacs are also developed in connection with the 

 larynx in many of the Apes. 



Nervous System. The brain of Mammals (Fig. 1214) is 



M M 2 



