Il MOUTH AND TONGUE 61 
be found at least traces of more cusps. Now in some of them 
we may be dealing with instances of a complete tooth change ; 
the suppression, save for one tooth, which is found in Marsupials, 
was probably not developed in at least some of these early 
mammals. The simplicity may therefore have been preceded 
by complexity, and may have been merely an adaptation to an 
insectivorous diet. 
Alimentary Canal—The mouth of the Mammalia is remark- 
able for the fact that with a few exceptions, such as the Whales, 
there are thick and fleshy lips. The 
office of these is to seize the food. 
The roof of the mouth is formed by 
the “hard palate” in front, which 
covers over the maxillary and pala- 
tine regions. This region is often 
covered with raised ridges, which 
have a symmetrical disposjtion, and 
are particularly strong in Ruminant 
animals. They are much reduced in 
the Rodents, where the anterior part 
of the palate is ill-defined owing to 
the way in which its sides fade into 
the lateral surface of the face. It 
has been shown that these ridges, 
in the Cat at least, develop as | ; 
“WP Fic. 40.—Palatal folds of the Raccoon 
separate papilliform outgrowths, and (Procyon lotor). p.p, Papillapala- 
it has been suggested that these tina; 7.p, palatal folds. (From 
: oo i Wiedersheim’s Structure of Man.) 
papillae, which later become united 
to form the ridges, are the last remnant of palatine teeth such 
as occur in lower vertebrates. 
The tongue is a well-developed organ, usually playing a 
double part. It acts as an organ of prehension, especially in 
such animals as the Giraffe and the Anteater, where it 1s 
long and protrusible beyond the mouth for a considerable dis- 
tance. It also carries gustatory organs, which serve for the 
discrimination of the nature of the food. Beneath the tongue 
there may be a hardish plate, known as the sublingua. This is 
especially prominent in the Lemurs, where it projects as a horny 
structure below the tongue, and has an independent and free tip. 
It is supported in some of these animals by a cartilaginous 
