52 PULPS AND SACS OF THE HUMAN TEETH. 



ings, communicating with small sacs, into which fine bristles may be passed. 

 At the third month the sacs of the second molars may be seen communicating 

 with the cavity of the mouth by small holes. The openings of the remaining 

 sacs are soon closed by the mucous membrane of the mouth. 



"The sacs of the permanent teeth are also formed immediately from the 

 mucous membrane of the mouth, partly at the fourth month of foetal exist- 

 ence, partly towards the end of that period, partly at birth. Once only, in a 

 new-born child, I observed behind the most prominent edge of the gums 

 several openings which led to the sacs of the incisives and canines, and which 

 are usually already obliterated before birth." 



These are all the facts Arnold has recorded, and from them it appears that 

 he was acquainted at that time with the secondary dental groove, the ten milk- 

 follicles, and the ultimate closure of the latter. So far as we can judge from 

 his brief notice, he appears to have been unacquainted with the mode of for- 

 mation of the permanent follicles, supposing them to be formed immediately 

 (unmittelbar) from the mucous membrane of the mouth, an opinion which is 

 very prevalent among the continental anatomists. I can only account for the 

 openings he mentions in the new-born child by arrest of development, or by 

 supposing that he had observed a few of the Tartar glands of Serres (Glandes 

 dentaires, Essai, etc., p. 28), which are best seen at the period to which he 

 alludes. 



Having now mentioned all the facts which Professor Arnold has published, 

 I may be allowed to state that I had made out all the facts detailed in this 

 paper before I was aware that any of them had been on record ; that I had 

 given an account of them at the last meeting of the British Association, before 

 I knew of Professor Arnold's notice ; and that this paper was in the hands of 

 the Editor of the Edinburgh Med. and Surg. Journal before I had an oppor- 

 tunity of seeing the Salzburg periodical. 



I had also demonstrated the principal facts in the follicular stage of denti- 

 tion, in 1835, to Mr. Nasmyth, to whom I am deeply indebted for the infor- 

 mation he has given me respecting the anatomy and surgery of these organs, 

 and in whose cabinet I at that time deposited preparations illustrative of the 

 facts. 



