as indicative of the Age of the Animal. 
353 
word molar to those teeth which are not ■preceded by similar 
ones. The term premolar is therefore intended to signify 
the j9?'e-existence of otlier teeth in the situation of these molars. 
After describing the temporary incisors of tlie pig, he thus 
writes : " The other teeth of the first set are the deciduous 
molars, the teeth which displace and succeed them vertically are 
the premolars, the more posterior teeth which are not displaced 
by vertical successors are the molars properly so called."* Now 
the teeth of the six months' old pig, to which the reader's attention 
has been es])ecially drawn, arc not renewed. They may therefore be 
correctly called permanent teeth, and as such they are true molars. 
In the horse we have the analogues of the premolars, called in 
this animal ' the wolf's teeth.' It is probable that this name has 
been given them from their being small in size and tush-like 
in form ; the tush being designated the canine (dog's) tooth. 
The ox and sheep will also now and then be found to possess 
similar teeth, adding to the normal number, and hence termed 
in tliese animals the supernumerary molars. The existence of 
these teeth, however, in the horse, ox, and sheep is an exception, 
but in the pig it is the rule, there being comparatively few pigs 
in which they are not found. The premolars of the pig, icolf^s 
teeth of the horse, supjemumerary molars of the ox and sheep, are 
never renewed in any of these animals, if they should be removed 
naturally or be surgically extracted, thus agreeing in this par- 
ticular with the permanent teeth. 
It will be observed that, although not strictly correct according 
to Professor Owen's definition, I have retained the term, premolars 
for these teeth, which I have been induced to do because they 
stand in the front of or before the other molars. I have likewise 
adopted our usual veterinary nomenclature in designating the 
other molars temporary and permanent. Something like this 
arrangement was required, it being necessary to mark in an 
especial manner tliese particular teeth from the importance which 
evidently belongs to the period of their cutting. 
Another fact will likewise assist an investigator into the age 
of pigs, namely, the putting up of the first permanent molar at 
the age of six months. This tooth is marked 4 p. m. in fig. 49, 
because it is the fourth in situation. As one of these teeth 
exists now on either side of both the upper and lower jaws, an 
addition of four teeth is evidently made at this period. At nine 
months old, or very near this date, the pig has other important 
changes taking place in his teeth. The foetal incisors and tushes, 
which rarely fall before this period, notwithstanding they be 
worn to the gums, now give place to the permanent incisors and 
Cyclopaedia of Anatomy and Physiology, vol. iv. p. 903. 
