TRANSACTIONS OF THE SECTIONS. 121 



contagious, and that quarantine laws were of no avail in checking its 

 progress. 



The following information was communicated to Dr. Bowring, by a 

 physician of long experience, in answer to a series of direct queries. 

 The plague is indigenous in Egypt, never entirely absent, never im- 

 ported ; it frequently occurs spontaneously, and cordons afford no se- 

 curity against its diffusion. While contact vei'y frequently does not 

 produce it, and it is not occasioned by linen which has been exposed 

 to the infection, the most cautious often suffer from it. Free ventila- 

 tion is effective in checking the disease, and when a number of per- 

 sons exposed to its influence remove from the infected spot, the mor- 

 tality amongst them becomes much diminished. 



On the Origin and subsequent Development of the Human Teeth. By 

 Mr. GooDsiR. 



The author has observed dentition commence by the formation of 

 what he denominates the primitive dental groove, on the floor of which 

 the rudiments of the pulps of the milk teeth appear as globular or co- 

 nical papillae ; septa afterwards pass from the outer to the inner side of 

 the groove, between the papillae, and thus each of the latter becomes 

 situated in an open-mouthed follicle, which is the primitive condition of 

 the future sac. After the formation of the milk follicles, the lips of the 

 groove still remain prominent ; and when in this condition Mr. Goodsir 

 denominates it tlie secondary groove. The rudiments of the ten anterior 

 permanent teeth appear as little depressions in the secondary groove, 

 internal to the mouths of the milk follicles. The papillae of the milk 

 teeth noAv begin to be moulded into the form of pulps, a change which 

 is synchronous with the closure of the mouths of the follicles by two or 

 more laminae, which agree in number, shape, and position with the cut- 

 ting edges and tubercles of the future teeth. The lips and walls of the 

 secondary groove now adhere, except in the situations of the ten de- 

 pressions for the permanent teeth, and for a small extent posteriorly on 

 each side, where a portion of the primitive dental groove remains in 

 its original condition. In this portion the papillae and follicle of the 

 first large molar tooth appear, and, after it closes over, the lips of the 

 secondary groove above it adhere, but not the walls ; so that there is 

 in this situation a cavity which produces the sacs of the two posterior 

 permanent molars. The first large grinder may, therefore, be con- 

 sidered in some measure a milk tooth. The author observes, that den- 

 tition begins, and is always in advance, in the upper jaw, except in the 

 case of the incisive teeth, which, although they appear first, are later 

 in coming to perfection. This he explains by the tardy development 

 of the lateral elements of the intermaxillaiy system. The author di- 

 vides dentition into three stages. The first is one with which the au- 

 thor states anatomists have hitherto been unacquainted, — viz. tlie folli- 

 cular. The second and third they are familiar with — the saccular and 

 tlie eruptive. From his researches, he concludes that the human teeth 



