178 



GEOLOGY. 



back-bone. You see the opening which 

 is filled with the spinal marrow. In 

 Fig. 98 you see the brain and spinal 

 marrow of man, showing how the nerves 

 branch out from the spinal marrow in 

 the vertebral column. This column dif- 

 fers much in length and arrangement 

 in different animals, being, for instance, 

 vastly longer in the serpent than in man, 

 and having a number of vertebrae in pro- 

 portion to its length. The vertebrata 

 have four grand divisions mammals, 

 or those that suckle their young, birds, 

 reptiles, and fishes. These are repre- 

 sented in Fig. 99. For the most part, 

 it is in this sub-kingdom that we have 

 the greatest complication of structure, 

 and with it the highest manifestations 

 of life. Intellectual qualities appear 

 here with their greatest prominence, 

 especially in those portions that ap- 

 proach to man ; and in man, the highest 

 of mammals, not only is there superior- 

 ity in degree of intellect, but there are 

 superadded powers, making his intel- 

 lect different in kind as well as in de- 

 gree, thus linking him with the Infinite, and showing the 

 significance of the expression, made in the image of 

 God. Little have the vertebrata contributed of material 

 for earth-making, but they are almost wholly zoological 

 in their relations, presenting in this respect an extreme 

 contrast to the lower orders of animal life, the protozo- 

 ans and the radiates. The relations of the vertebrates 

 and the higher orders of the vegetable world, the endo- 

 gens and the exogens, are very obvious, and accordingly 

 we find in the life-record of the rocks the evidence of 

 their introduction together upon the world's arena, the 



