PULPS AND SACS OF THE HUMAN TEETH. 43 



canines, and bicuspids ; the two posterior for that of the second 

 and third molar,* the coronoid process acting the part which 

 the maxillary tuberosity did in the upper jaw. 



SECTION III. 



1. On the Division of Dentition into Stages. As dentition 

 is a process, not only very complicated in its details, but of 

 very lengthened duration, extending over nearly eight months 

 of intra-uterine, and above twenty years of extra-uterine 

 existence, the understanding and further investigation of it 

 may be facilitated by dividing it into stages. The most 

 natural division, one which is not artificial, but clearly indi- 

 cated by the phenomena themselves, is into three stages, 

 according to the position of the pulp in relation to its con- 

 taining cavity 1st, follicular stage ; 2d, saccular ; 3d, eruptive. 

 We ought probably to consider, as anterior to the follicular, 

 the papillary stage t during which the follicle or sac does not 

 exist, and the future pulp is a simple papilla on the free surface 

 of the gastro-intestinal mucous membrane. As this stage, 



* The cavities of reserve are occasionally somewhat undefined, two or three 

 being conjoined, particularly posteriorly. Sooner or later, however, they 

 become distinct. The great cavity frequently stretches forwards over the sacs 

 of the milk-molars. 



f Most anatomists have supposed the germs of the teeth to appear as shut 

 sacs, full of a fluid, the pulps being formed by inspissation of the latter, or by 

 development from the walls of the former. Neither Mr. Hunter nor Mr. Bell 

 has stated anything very definite on this subject. The pulp must be con- 

 sidered as the principal part of the organ, and as the element which appears 

 first. The sac is a mere subsidiary part, supplied for purposes of development 

 and nourishment. Handbuch der Anatomic des Menschen, von. H. Hilde- 

 brandt, besorgt. von E. H. Weber, Erster Band, p. 212 ; Handbuch der 

 Entwickelungs-geschichte des Menschen, von Yalentin, p. 482 ; Arnold, Salz- 

 burg Medicinisch-Chirurgisch Zeitung, 1831, Erster Band, p. 236 ; Cruveilhier, 

 Anatomie Descriptive, vol. i. p. 518 ; Serres, Essai sur V Anatomie, etc., des 

 Dents, p. 59; Ph. Fr. Blandin, Anatomie du Systeme Dentaire, etc., p. 87; 

 Blake, Essay on the Human Teeth, p. 2. 



