LUNGS OF MAMMALIA. 577 



one or two notches. In another Kangaroo I found the right lung 



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divided into four lobes, the left into two. The azygos lobe is 

 large in consequence of the length of the chest in the Kangaroos, 

 and the distance of the heart from the diaphragm : it is three- 

 sided, one side convex, the second concave and applied to the 

 pericardium, the third side concave, and in contact with the 

 diaphragm. In the Potoroo the left lung is unilobate with a 

 fissure on the anterior or upper edge ; the right lung has two or 

 three deep fissures ; the azygos lobe is elongated, pointed, and 

 trihedral, as in the Kangaroo. In the Petaurists and Phalangers 

 the right lung is trilobate, the left bilobate ; there is also a lobulus 



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azygos. The Koala has the lungs similarly divided, and not 

 simple as in the Wombat. In the Opossums, Dasyures, and 

 Perameles the right lung is usually trilobate (bilobate in Didel- 

 phys bracliyurn^), and with the usual azygous appendage : the left 

 lung is commonly divided into two, but is sometimes entire, as in 

 the Perameles and Didelph. bracliyura. In all the marsupials the 

 rio-ht lung is the largest, owing to the oblique inclination of 



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the heart to the left side. 



In the order Rodentia a tracheal structure, recalling the early 

 division of the tube in Reptiles, is present in the Cape Jerboa 

 (Helamys) : the windpipe is divided a little beyond the larynx 

 into two canals by a median septum, as if the bronchi there 

 began, and were continued, adhering, some way before diverging 

 to the lungs. In the Coipu (^J\fyopotamus^) the extrapulmonary 

 bronchi are each one-third the length of the undivided trachea. 

 The right lung has four lobes, the left three : the same division 



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obtains in Dasyprocta : in Ccelogenys the lungs have been seen to 

 be still more divided. In Orycterus capensis the left lung is un- 

 divided, the right has four lobes. In the Water Vole (Arvicola) 

 the left lung has two lobes, the right four. In the Porcupine the 

 rio-ht lung has four lobes besides the azvgous lobule. In the 



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Hare th'e right lung has four lobes, the left two. 



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The thoracic cavity and the lungs are comparatively large in 

 the Mole : in this Insectivore, as in the Hedgehog and Shrews, 

 the right lung has four lobes, the left one lobe : in the Chryso- 

 chlore the left lung has two lobes. In true Bats the luno-s are 



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large, and with one or two shallow fissures : in Pteropus the right 

 lung has three lobes, the lower one extending to the place of the 

 azvgous lobule : the left lung is bilobate : in this genus, as in 



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Galeopithecm, a few upper rings of the trachea are entire, fig. 460 : 

 the ends of the slit ones meet behind. 



In Dasypus Peba the right lung has three lobes, the left two : 

 VOL. nr. r p 



