135 



a seclion, in an enquiry into the development of this part of the 

 skeleton ; consequently the cranium, auditory cavities, orbits, 

 m.)Ulh, and nasal fossae, which afford lodgement to the brain, 

 the organs of hearing, vision, tasting, and smelling ; as also those 

 parts of the bones o[ the head, which are subservient to the 

 function of mastication ; will successively come under our con- 

 sideration ; and will naturally lead to some observations, respect- 

 ing the changes, which the head in general undergoes, in con- 

 sequence of the clianges of its particular parts. 



SECTION I. 



CRANIUM. 



The proportion of the cranium to other parts of the skeleton, 

 and of the several regions of tlie cranium to one another, at dif- 

 ferent periods of life, forms a curious and interesting object of 

 inquiry. The rapidity of its growth, when compared with al- 

 most all the other cavities of the head, and with the entire 

 skeleton, has, at all times, attracted considerable attention, and 

 been a fruitful source of speculation ; but the relations, that exist 

 between the development of its different parts, have been, in a 

 great measure, overlooked. 



Between the third and fourth week after conception, the cranium 

 is observed. It has then the appearance of a vesicle containing the 

 infant brain ; and forms, at least, one half of the whole embryo, 

 and the entire of the head : for the other cavities cannot be distin- 

 guished. By degrees, the face is developed ; but, for a long time, 



