59° 



THE POPULAR SCIENCE MONTHLY. 



The elements composing the nutritive case are the jaws, ribs, and 

 pelvic girdle. These, like the spinal elements, are subject to great 

 modification, owing to the immense range of variation to which their 

 specializations are subjected. The difference in the facial develop- 



Fig. 2. 



ments can well be imagined by calling to mind the various coun- 

 tenances of animals, from the fish to man. The angle of the face is 

 simply and properly, I think, indicated by the relation expressed by 

 two lines : the first, or base line, corresponding to the axis of the 

 body; the other, diverging, or face line, drawn from the anterior 

 margin of the upper jaw, over the centre of the forehead. The rela- 

 tion and angles formed by these two lines, and their intersections thus 

 indicated, express the relation and comparative development at the 

 union of the two primitive tubes, the neural, or skull, and hemal (face), 

 at the anterior extremity or head of a vertebrate animal. 



As before stated, authors have hitherto established the base-line 

 from the floor of the nostrils, to the articulation of the occipital bone 

 to the vertebra?. This is a grave error, and one, no doubt, that has 

 contributed its share to depreciate the subject as an index to the men- 

 tal caste of a vertebrate animal. For, by adopting this method, we 

 are subject to the enormous error of ninety degrees in passing through 

 the sub-kingdom, all of which we lose, little by little, as we ascend the 

 scale of animals of this type, or form of structure. And yet they make 

 this application through the entire vertebrate series. Yet, by referring 

 to the cut, we find the face of the lowest class of the type, the fish, to be 

 in direct line with the dorsal surface of the animal, and hence the base 

 and diverging lines are parallel ; while, in the highest of the type, 

 that of man, the face is in line with the ventral or abdominal surface. 

 Again, after effecting a grand variation of one hundred and eighty 

 degrees, or the half of a circle, the two lines are once more parallel. 



What, then, are the factors in the phenomena of the great change 

 of the aspect of the face, with such a modification of its constituents, 

 from a line of the dorsal to that of the abdominal surface, all of which 

 is effected by almost imperceptible gradations, as we ascend the series 

 from the fish to man ? It is by the modification of the anterior ex- 

 tremities of these cranio-vertebral canals in the development and in- 

 crease of the cerebral hemispheres, which is that part of the brain that 

 is recognized as the seat of thought, and their influence upon other 



