STRUCTURE AND GROWTH OF INCISOR TEETH 83 
but by staining (e.g., with acid fuchsin), the remains of these 
may be made out in less calcified spots in the matrix. Evidently 
the odontoblasts and other tissues of the pulp which move with 
the dentine, become more and more compressed at the narrow- 
ing apex of the pulp-chamber, and finally there is this irregular 
deposit of secondary dentine between them, which serves to 
obliterate the pulp-chamber. As the tooth moves out, this 
process is constantly going on, just in advance of the occlusal 
surface, and keeps pace with the process of attrition. 
It is interesting to note the rate at which the teeth are in- 
creased in length during their formative period and prior to 
attrition. 
Upper Lower 
mm. mm. 
iL releinedralhal,. .. o's Sheba eaten eile ete am hag mn a ze 2.3 3 
AMG SO CPR ee Rae os. Sin eenctr ne aa Gi bid ct aaa a 3.6 5 
CLAN, Sig © | CLONER ER ENA ean Ine Jc ree teasers MR te thi stcegs dee a ae eee 5 7-8 
ORG aiSe OG Merry ee cues cP ou sb rae Ane ai cee e Se Ti 11 
Average growth 0.52 mm. and 0.88 mm per day 
As will be seen later, this exceeds the rate at which the mature 
tooth continues to grow out. 
DESCRIPTION OF MATURE TOOTH AND TOOTH-FORMING ORGANS, 
IN FIVE-MONTH ANIMAL 
In the mature tooth, the general relations are shown in figure 
25, made from a photograph of a decalcified section of the upper 
tooth of a 5-month animal. The regular curved outline is seen, 
with the greater proportion of the length imbedded within the 
jaw, and only a small part projecting. The formative end 
lies within an investment of bone belonging to the maxilla. 
At this end the dentine is very thin and the pulp greatest in 
amount. As one goes forward, the dentine increases regularly 
in thickness while the pulp-chamber becomes smaller and smaller. 
The vacuolated appearance at the anterior end of the chamber 
is due to shrinkage of the pulp tissue during fixation. The 
enamel has been lost in the process of decalcification except over 
the basal third. Numerous blood-vessels are seen within the 
pulp. 
