598 CLASS XVII. 



(superior or sensitive) roots with the sympathetic nerve, as the 

 investigations of Wutzer, Mueller, Eetzius, and Mayer have 

 demonstrated^. 



The skin of mammals is covered with hair as the rule ; some 

 have horny scales as Manis, or bony plates as the armadillos (the 

 genus DasT/pus^), or spines [Erinaceus, Hystrix, Tachyglossus, &c.^). 

 The sense of touch is variously developed in the extremities of the 

 limbs in the different species, according as the feet serve only for 

 progression and standing, or for seizing also. In the apes, which 

 in this respect are the most privileged, the hand is indeed much 

 less adapted for feeling than in man, who in his erect posture and 

 gait can move and apply his fore limbs for the sense of touch more 

 commodiously. The whiskers which are attached to the lips, serve, 

 like the fleshy appendages at the jaws of some fishes (see above, 

 p. 46), to give warning of external obstacles. Branches of the 

 fifth pair of nerves are distributed to their roots. Cats are rendered 

 unable to catch mice when these whiskers are removed, and various 

 experiments have shewn, that rabbits without the assistance of their 

 eyes can by means of these hairs find an outlet in narrow passages*. 

 Similarly, the membrane, richly supplied with nerves, which is 

 extended between the fingers of the hand in the bats, serves for the 

 avoidance of external obstacles dm-ing flight, whilst the experiments 

 of Spallanzani have shewn that neither smell, nor sight, nor 

 hearing are necessary for this. 



Taste is more highly developed in mammals than in the rest of 

 the vertebrate animals. The tongue is fleshy, consists of many 

 muscles which mutually decussate, and thus are able to effect a 

 great variety of motion. We may here conveniently describe the 

 bony apparatus to which the tongue with its various muscles is 



^ See Retzius, Meckel's Archiv, 1832, s. 260, 261, with a figure of the con- 

 nexion of the tenth spinal nerve with the sympathetic in the horse, Tab. i, fig. 10 ; 

 Wutzer in Mueller's Archiv, 1834, s. 305 — 310. 



2 Compare H. Meyer Ueher den Bau der Haut des GurteltMers, Mueller's 

 Archiv, 1848, s. 226 — 232. True bony plates are situated in the coriiim, which forms 

 under them a very thin layer only ; horny scales are situated in the epidermis, 



^ See F. Cuvier Recherches sur les epines du, pore-epic, ' Nouv. Annales dii Mus. L 

 1832, pp. 409 — 439; C. J. A. BcECKH. De spinis Hystricum DUscrtatio, Berohni, 

 1834, 4to. 



* G. Vrolik Over het nut der hievels hij viervoetiye dieren, Amsterdam, 1800, 

 8vo. 



