ARCHITECTURE OF THE SKULL 23 



and these ridges of bone, when the skull is formed 

 with what we call a due regard to security, give 

 an extension to the forehead. 1 



In concluding this survey of the architecture of 

 the head, let us suppose it so expanded that we 

 could look upon it from within. In looking up 

 to the vault, we should at once perceive the appli- 

 cation of the groin in masonry; for the groin is 

 that projection in the vault which results from 

 the intersection of two arches running in different 

 directions. One rib or groin extends from the 

 centre of the frontal bone to the most projecting 

 part of the occipital foramen, or opening on the 

 back of the head; the other rib crosses it from 

 side to side of the occipital bone. The point of 

 intersection of these two groins is the thickest 

 and strongest part of the skull, and it is the most 

 exposed, since it is the part of the head which 

 would strike upon the ground when a man falls 

 backwards. 



What is termed the base of the skull is strength- 

 ened, if we may so express it, on the same prin- 

 ciple : it is like a cylinder groin, where the rib 

 of an arch does not terminate upon a buttress or 

 pilaster, but is continued round in the completion 



1 Although they are solid arches connected with the building 

 of the cranium, and bear no relation to the surfaces of the brain, 

 the early craniologists would have persuaded us that their forms 

 correspond with the surfaces of the brain, and indicate particular 

 capacities or talents. 



