484 ORGANS OF DIGESTION. 



In the preceding cartilage are found many small glands, 

 grouped about in different parts of it. They were discovered 

 within a few years past by M. Serres,* of Paris; are about the 

 size of a millet seed, contain a whitish fluid, and when examined 

 by the aid of a microscope do not appear to have any distinct 

 opening or duct, in consequence of which they must be punctured 

 in order to expel their contents. The largest of them are on the 

 internal side of the gum near the molar teeth. 



According to their discoverer, these glands serve to lubricate 

 the dental cartilages of the infant, but after the protrusion of the 

 teeth they secrete the substance commonly called Tartar, and 

 heretofore falsely attributed to the saliva. Their secretion being 

 of a fatty nature, keeps up the high and brilliant polish which the 

 teeth have till middle age; it being afterwards altered, the teeth 

 then become more dull and yellow. Salivation produces an ex- 

 cessive secretion and deposite of tartar from these glands. J. F. 

 Meckel states, that he has never been able to discover them till 

 towards the period of dentition, from which he is rather induced 

 to consider them as a morbid production depending upon irri- 

 tation, and probably not differing from little abscesses. 



SECT. V. DENTITION. 



Infants have a set of teeth called Deciduous, from their being 

 lost after a certain period of time. Their whole number is twen- 

 ty, ten in each jaw, consisting on either side of two incisors; one 

 cuspidatus; and two molares, having a shape corresponding with 

 that of the large grinders in the adult. Several of these teeth 

 fall out about the seventh year, and all of them have disappeared 

 about the fourteenth. The time of their first protrusion through 

 the gums is variable, but may, as a general rule, be stated at 

 from the sixth to the eighth month after birth. They appear 

 commonly in pairs. The pairs of the lower jaw have prece- 

 dence in their protrusion; and are immediately followed, suc- 

 cessively, by their congeners in the upper. The order of pro- 

 trusion is as follows : 



The two central incisors, from the sixth to the eighth month ; 



The two lateral incisors, from the seventh to the tenth month ; 



* Loc. cit. 



