MAMMALIA. l' I ''> 



CHAPTER IX. 

 Class V. MAMMALIA. * 



War in-blooded, lifiiri/ minimi* n-itlt double occipital condyle. TJi<-;f 

 are viviparous and suckle their ijouivj with the secretion of milk 

 (mammary) glands. 



As opposed to Birds, Mammals are adapted, by the similar struc- 

 ture of the two pairs of extremities, to live principally on land. 

 There are, however, in this class also forms which are fitted in 

 various degrees for an aquatic life, and even live entirely in water, 

 and again forms which move and find their food in the air. 



The surface of the skin is rarely quite smooth as in the Cetacea, 

 but is traversed by numerous curved, . spiral, and partly crossing- 

 furrows, and in many places (sole of foot, ischial callosities) is thick- 

 ened and indurated, so as to form firm, horny plates. 



The hairy covering is to Mammalia (named " Haarthiere " by Oken), 

 what the plumage is to Birds. Hairs are never entirely absent : 

 even the huge aquatic forms and the largest of the tropical terrestrial 

 species which seem to be naked, possess hairs on certain parts of the 

 body ; e.g., the Cetacea have short bristles, at least on the lips. Hairs, 

 like feathers, are epidermal structures (fig. 666.) The bulbous root is 

 placed on a vascular papilla (pidpa), at the bottom of a pit, which 

 projects into the cutis and is lined by epidermal cells (hair-follicle) 

 while the upper part, or shaft, projects freely on the surface of the 

 skin. Two kinds of hairs may be distinguished, according to the 

 strength and rigidity of the shaft, viz., contour hairs and woolly 

 hairs. Woolly hairs are delicate and curled, and surround in larger 

 or smaller numbers the base of each contour hair. The finer and 

 warmer the fur, the more numerous are the woolly hairs (winter-fur). 

 When the contour hairs have a greater strength they become bristles, 



* Job. (Jh. D. v. Schreber, "Die JSiiugethiere in Abbilduugen nach cler Natur 

 mit Beschreibungen, fortgesetzt von Joh. Andr. Wagner," Bd. I. VII., unl 

 Suppl. I. V. Erlangeii und Leipzig. 17751855. 



E. G. St. Hilaire et Fred. Cuvier, " Histoire naturelle dcs Mammiferes," 

 Paris, 18191835. 



C. J. Temmink, " Monographic de mammalogic." Leiden, 18251841. 



R. Owen. ' Odoutography," 2 vol. London, 1840 18-i5. 



Blasius. "Die Saugcthiere Deutschlands " 1875. 



G. Giebel, " Die Saugethiere in zoologisch-anatomischer uud palaontologisches 

 Hinsicht." Leipzig, iS5U. 



A. E. Brehm. llluslrirtes Thierleben " L, II., nnd III. 



And. Murray. "The Geographical Distribution of Mammalia." London, 



VOL. II. 18 



