88 INTRODUCTION. 



The tongue of mammalia is always fleshy, and 

 attached to a bone named hyoid (os hyoides), which 

 is composed of several pieces, and suspended to the 

 cranium by ligaments. 



Their lungs are two in number, divided into lobes, 

 and composed of an immense multitude of small 

 cells ; they are invariably suspended, without adhe- 

 sion, in a cavity formed by the ribs and diaphragm, 

 and lined by the pleura. Their organ of voice is 

 always at the superior extremity of the trachea or 

 windpipe ; and a fleshy prolongation, called the cur- 

 tain of the palate (velum palati), establishes a direct 

 communication with the back part of the nostrils. 

 As mammalia reside in general on the surface of the 

 earth, they are less exposed to alternations of heat 

 and cold, and, therefore, the covering given them is 

 only of moderate density ; yet varying from a close 

 fur, in high latitudes, to a very scanty spread of hair 

 in the tropics ; and cetacea, entirely confined to the 

 waters, are alone deprived of every excressent pro- 

 tection. * 



* We think this abbreviated review of Baron Cuvier's 

 generalities on this subject, together with an occasional glance 

 at the excellent Introduction to a Version of the Animal 

 Kingdom, commenced, we believe, by William Macgilli- 

 vray, A. M., with copious additional observations, sufficient 

 for our popular series, referring those, who are desirous of 

 more complete information, to the two works here mentioned, 

 to Griffith's Animal Kingdom, and to Professor Owen's papers 

 before noticed. We refer also to the excellent description of 

 Mr. Martin, in his Nat. Hist, of Quadrupeds. 



