330 THE STORY OP THE EARTH AND MAN. 



Spencer and Darwin occasionally see this difficulty, 

 though they habitually neglect it in their reasonings. 

 Spencer even tries to turn one part of it to account as 

 follows : 



" Suppose the head of a mammal to become very 

 much more weighty what must be the indirect re- 

 sults ? The muscles of the neck are put to greater 

 exertions; and the vertebrae have to bear additional 

 tensions and pressures caused both by the increased 

 weight of the head and the stronger contraction of 

 muscles that support and move the head.'" He goes 

 on to say that the processes of the vertebrae will have 

 augmented strains put upon them, the thoracic region 

 and fore limbs will have to be enlarged, and even the 

 hind limbs may require modification to facilitate loco- 

 motion. He concludes : " Any one who compares the 

 outline of the bison with that of its congener, the 

 ox, will clearly see how profoundly a heavier head 

 affects the entire osseous and muscular system." 



We need not stop to mention the usual inaccuracies 

 as to facts in this paragraph, as, for example, the 

 support of the head being attributed to muscles 

 alone, without reference to the strong elastic liga- 

 ment of the neck. We may first notice the assump- 

 tion that an animal can acquire a head " very much 

 more weighty " than that which it had before, a very 

 improbable supposition, whether as a monstrous birth 

 or as an effect of external conditions after birth. But 

 suppose this to have occurred, and what is even less 

 likely, that the very much heavier head is an advan 



