VESTIGIAL PARTS. 73 
normal, the tumour occupying the position which should 
have been filled by the missing teeth. 
That imperfectly developed teeth give rise to tumours 
is indisputable ; for instance, the teeth before they make 
their appearance above the gums are enclosed in a bag, or 
follicle, formed partly of fibrous tissue or bone. Occasion- 
ally teeth which should normally be cut and take their 
position in the dental series, remain hidden beneath the 
FIG. 35.—A composite odontome from a Horse, weighing 
-700 kilograms. 
gums; in such cases fluid accumulates between the 
aberrant tooth and its capsules, forming a tumour known 
as a follicular cyst (fig. 34). 
Sometimes the germs of several teeth coalesce and 
give rise to an ill-shaped mass of dental tissue known as 
a composite odontome (fig. 35): in due course this 
abnormal conglomeration of tooth tissue attempts to 
rise above the gums, or becomes erupted like an ordinary 
