HORN AND BONE. 291 



animals, where a black hoof and a black horn are 

 always of firmer structure than those that are of a 

 light colour : the bills and claws of many young birds, 

 which have them dark when full grown, are light- 

 coloured, and so are the hoofs of newly cast calves, and 

 in that state they are soft. On the other hand bones 

 are always the more firm and compact the whiter that 

 they are. More than one half of the average of horny 

 substances is carbon, the same matter as the diamond, 

 though in combination with other substances ; while in 

 bones, nearly one-half consists of salts of lime; and as 

 those vegetable substances that contain the greatest 

 quantity of carbon, are, generally speaking, the hardest, 

 it may be that the strength of black horn depends on a 

 greater proportion of carbon, in the same manner that 

 white bone is more compact from containing a greater 

 proportion of lime. 



The bill of the woodpecker is straight and angular, 

 as long as the head of the bird, (about two inches), 

 compressed at the sides, having a strong and permanent 

 culmen or ridge on the upper side of the upper mandible, 

 tapering gradually to the point which is wedge shaped. 

 The base of the bill, and the space round the eyes are 

 deep black ; and black bristles are retroflected backward 

 over the nostrils. The upper part of the head and 

 the moustachios are, in the male, of a bright blood red, 

 which, however, as is often the case with the bright 

 colours in birds, only marks the tips, the bases of the 

 feathers being bluish grey. The nape, the upper part 

 of the back, and the wing covers, are a warm but not a 

 very brilliant green, resembling sap green with the least 

 trace of brown. The lower part of the rump and the 



