PULPS AND SACS OF THE HUMAN TEETH. 47 



as indicative of the existence of the rudiment of a bone also, 

 especially when the interesting antagonism, which I will show 

 exists between it and the lateral lobules, is taken into con- 

 sideration.* 



As the object of this part of my paper, however, is not to 

 discuss the osteogenesis of the human head, but to explain 

 why the inferior incisive teeth, although later in their appear- 

 ance, are yet more rapid in their progress than the superior, 

 I shall now recall some circumstances formerly detailed re- 

 garding the development of the three intermaxillary lobules, 

 immediately before and for some time after the appearance of 

 the incisive papillae. 



During the seventh week the three lobules are equal, and 

 there is no appearance of either the upper or lower incisive 

 teeth. 



During the eighth week the median lobule has increased 

 relatively, and the laterals only absolutely ; while as yet 

 there is no appearance of either the upper or lower incisives. 



During the ninth week the median has diminished re- 

 latively, and in the transverse direction ; the laterals again 

 have increased relatively and also in the transverse direction. 

 This relative transverse increase of the lateral lobules is syn- 

 chronous with the first appearance of the upper incisives. The 

 inferior incisives are so indistinct at this time, as to be recog- 

 nised with difficulty as slight bulgings on the floor of the 

 dental groove. 



During the next fortnight the relative size of the median 



* A small cartilaginous body exists in the median intermaxillary lobule of 

 the child at birth. It is situated in front of the inferior orifice of the naso- 

 palatine canal, and between the mucous membrane and periosteum. 



The median intermaxillary lobule exists in the adult palate, and may be 

 felt behind and between the central incisives. Median intermaxillary bones 

 and cartilages exist in certain of the lower vertebrata. 



The bar-like vomer of the human embryo at the sixth and seventh week 

 reminds the anatomist of the adult vomer of the lower vertebrata. 



