623 



A few other Mammals show partial deposits of scale-shaped 

 cuticle. Thus, in the tail of the Beaver the epiderm is disposed 

 in hard scale-like plates, the anterior margins of which project 

 obliquely inwards, and develop small pointed processes which pass 

 into corresponding depressions of the derm. In the great Flying 

 Dormice of Africa (Anomalurus) there is a double row of alternate 

 overlapping horny plates at the under part of the base of the tail, 

 reminding one by their size and strength of the scales of Manis. 



§ 363. Nails, Claws, and Hoofs. — The derm covering the ends 

 of the digits, in Man, is closely connected or confluent with the 

 perioste at the back of the last phalanx, and forms near its base a 

 crescentic groove or ( nail-bed,' from the ridged and highly vascular 

 surface of which a solution of epidermic material exudes, which 

 material formifies as cells, at first vertical to the surface ; then, 

 when pushed off by a succeeding precipitate of cells, becoming 

 flattened, and ultimately condensing or coalescing into the horny 

 plate termed the ' nail.' 



In the hoofed quadrupeds the ridged or laminate vascular derm 

 or dermo-perioste extends over the fore and lateral parts of the 

 last phalanx, and similarly provides it with a thick hard horny 

 wall, in great part of which the primitive cells have condensed 

 into fibres perpendicular to the plane by which the superincumbent 

 weight is transferred to the ground. In the Horse the formative 

 lamella? are shown in fig. 17, at i: ; the resulting hoof being 

 turned off to expose the horny lamella?, ib. 3, which interlock with 

 the vascular lamellas. From the greater part of the derm cover- 

 ing the under surface of the foot horny matter arranged as vertical 

 fibres is also formed, completing, with the denser front and side 

 walls, the case called ( hoof.' The fibrous epiderm on the sole of 

 the bisulcate foot of the Ruminant is very thick, but less dense 

 than in the soliped. Further particulars of the structure of the 

 Horse's hoof are given at pp. 39-41. 



In Carnivora the base of the last phalanx forms a ( nail-bed ' 

 much deeper than in Man, a plate of bone being reflected forward 

 like a sheath for the base of the terminal, prominent, and pointed 

 part of the phalanx. The dermo-perioste of this bed develops a 

 very dense horny sheath covering the claw-core, and reciprocally 

 received at its base within the ' bed ' or sheath formed by that 

 part of the ungual phalanx. For the form of such ' claw ' in the 

 Felines, and the muscular and elastic structures connected there- 

 with, see pp. 69, 70, and fig. 36. The maximum of claw-develop- 

 ment is, however, presented by the Armadillos (vol. ii. figs. 272, 

 276), the Sloths (ib. fig. 280), and the Anteaters (ib. fig. 263): in 



