302 On the Teeth of the Ox, Sheep, and Pig, 
up, corresponding in number with the temporary set of teeth. For 
example, in the ox there would be eight of these representing tlie 
eight temporary incisors, and twelve representing the number of 
the temporary molars, three of the latter being placed on either 
side of the upper and lower jaws. I may here say that, for the 
sake of perspicuity, my account will be confined to the teeth 
of the lower jaw — incisors and molars. 
These papilla? gradually increase in size, and acquire the shape 
of the future teeth. While this is going on, partitions are formed 
across the groove between the papillae, by which they become 
separated from each other. Tiiese partitions subsequently form 
part of the bony sockets, as existing between the teeth when 
they are fully developed. The rising and growth of the papillae 
constitute the first or papillary stage (2, 3, fig. 12). 
By the formation of the partitions each papilla is placed in a 
separate cavity of a square shape, called a follicle ; and thus 
we see that the follicular stage now exists (4, 5, fig. 12). Con- 
currently with the formation of the follicle, small growths also 
take place from the membrane just as it dips into the cavity. 
These, as lids to the follicle, l)y their further enlargement cover in 
the papilla, and by their subsequent union place it in a closed 
sac or bag. This is the saccular stage (6, 7, and 8, fig. 12). 
The formation of the different component parts of the tooth now 
goes on with greater rapidity, and after a certain state of com- 
pleteness, the young tooth grows upwards, and penetrates both 
its sac and the gum which by this time also covers it, constituting 
thereby the eruptive stage, commonly known as the cutting of 
the tooth. (9, fig. 12.) 
Returning to the diagram : fig. 4 shows a slight folding in- 
wards of the membrane of the primitive dental groove near to 
the lid on the right side ; this is made more apparent in fig. 5. 
In fig. 6 it is marked e, and also in fig. 9, where we observe 
that the folded membrane considerably altered in form, as also 
increased in size, having a projection from its bottom part — 
the papilla destined for the production of the permanent tooth, 
is detached from the follicle. The intermediate figs., 7 and 8, 
show the progressive advance and separation of this fold of 
membrane from that which lines the original groove. As one 
of these folds belongs to each follicle, so they are equal in number 
with the temporary teeth ; and thus each temporary tooth, while 
being formed, lays the foundation for its permanent successor. 
These have been called by Professor Goodsir "cavities of reserve, 
as they furnish delicate mucous membranes for tlie future forma- 
tion of the permanent teeth.""* As to the permanent molar teeth, 
* Todd and Bowman's Physiological Anatomy, pai t iii., p. 179. 
