32 NATURE'S TEACHINGS. 



boscis, require a corresponding supply of muscles, and conse- 

 quently a large surface of bone for the attachments of these 

 muscles. Now, were the skull solid in proportion to its 

 requisite size, its weight would be too much for the neck to 

 endure, however short and sturdy it might be. The mode of 

 attaining expanse of surface, together with lightness of struc- 

 ture, is singularly beautiful. 



Perhaps some of my readers may not be aware that the bone 

 of the skull consists of an outer and inner plate, with a variable 

 arrangement of cells between them. In many animals, such, 

 for example, as man, where the jaws are comparatively feeble, 

 and the teeth small and light, the size of the skull is practically 

 that of the brain, to which it affords a covering. The same 

 structure may be observed in the skull of the common 

 sparrow, where, as in man, the two bony plates are set almost 

 in contact. 



But in the elephant these external and internal plates are 

 set widely apart, and the space between them is filled with 

 bony cells, much resembling those of a honeycomb. They are, 

 in fact, just the same cells as those which exist in the skull of 

 man and sparrow, but they are very much enlarged, and in 

 consequence give a large surface, accompanied with united 

 strength and lightness. 



There are many other examples in the animal kingdom, but 

 our limited space will not allow them to be even mentioned. 



As to the vegetable examples of this principle, they are so 

 multitudinous that only a very slight description can be given 

 of them. 



I suppose that most boys have seen a " cane " (whether they 

 have felt it or not is not to the purpose), and some boys have 

 made sham cigars from pieces of cane. In either case they 

 must have noticed that the cane is not solid, but is pierced 

 with a vast number of holes, passing longitudinally through it, 

 and is, in fact, a collection of little tubes connected and bound 

 together by a common envelope. 



The Sugar-cane, if cut across, is seen also to consist of mul- 

 titudinous cells, which, however, are not hollow, but filled with 

 the sweet liquid from which sugar is obtained by boiling. 

 Then there are many of our common English plants, like the 



