344 Oh the TccLh of the Ox, Sheep and Puj, 
Fig. 42." 
quarters — adding to the difficulty of forming a correct opinion 
upon a few examinations, and without standards of comparison. 
Fig. 43 shows the front of the lower jaw of a sheep at two 
years and a half old, the intermediate period between the dates 
cited. Six permanent incisors are 
here seen well up ; the relative 
size of each of the three pairs is 
also nicely depicted. 
Another nine months will some- 
times elapse between the cutting 
of the third and the fourth pair. 
During this period, from daily 
attrition, the four central teeth 
will give increased evidence of 
wear. They will in many in- 
stances be flat on their surface, or 
it may be that this is worn into 
hollows. The amount of this 
change will necessarily be regu- 
lated by the management pursued, 
and the food upon which the ani- 
mals have been kept. Even in 
manger-fed sheep, wear will be 
apparent, and not unfrequently 
an open space will exist between 
the fangs of the central pair in 
particular, from the rising of the 
incisors in their sockets to com- 
pensate for their diminished 
length. 
In many districts, as on the 
heath lands of Norfolk, it often 
happens that long before the per- 
manent corner incisors are put up, 
the centrally - placed teeth are 
broken across their bodies, by 
the rough plants on which the 
sheep graze. Such animals are 
called " crones." The Norfolk 
heath-land farmer has to look well 
to his flock, and draft such sheep, 
as they daily lose condition and 
* Fig. 42. Side view of the lower jaw of a sheep at two years old; showing the last 
molar on a level with the others, the two anterior temporary molars replaced by 
permanent, and the third in the act of being changed, part of its body still adhering 
to the cum and capping the upper surface of the permanent tooth. Natural size. 
