220 COMPARATIVE MORPHOLOGY OF VERTEBRATES. 
The dorsal surface is usually covered with a soft epithelium, developed 
into papille of varying shapes, some being sensory in character, and 
some are occasionally (monotremes, felids) cornified. 
The skeleton of the mammalian tongue (hyoid apparatus) varies 
considerably. In its most complete development it consists of a body 
(copula of the hyoid and first branchial) in the median line, which bears 
two pairs of cornua. The anterior pair (lesser horns of human 
anatomy) are usually elongate, and consist of a series of ossicles (p. 101) 
connecting the body with the otic region of .the skull. . The second 
pair (greater cornua of man) are occasionally absent. In man the 
greater part of the anterior cornua is represented by. the stylohyoid 
ligament, the proximal portion being fused to the skull as the styloid 
process. 
Oral Glands. 
In the cyclostomes there is a large, so-called ‘salivary gland’ of 
unknown function, opening into the mouth on either side below the 
tongue. With this exception, glands are lacking from the mouths of 
aquatic ichthyopsida. With the assumption of pulmonate respiration 
and more terrestrial habits, the mouth is no longer constantly bathed 
with water and so glands appear, 
increasing in number and com- 
plexity in the higher forms. The 
secretion of these glands aids in 
moistening the food, and not in- 
frequently it is adhesive and is 
used in capturing the prey. In the 
mammals true salivary glands ap- 
pear. The saliva secreted by them 
: contains not only mucus, but also a 
ee ce et ee ae digestive ferment (ptyalin) which 
d, tooth; h, hyoid cartilage; /, labial glands; changes starch into sugar. The 
m, muscles; si, sublingual gland; ¢, tongue. : 
names of the various oral glands 
(labial, buccal, lingual, retrolingual, etc.) are roughly indicative of 
their position. 
In the terrestrial amphibia, snakes (fig. 215) and lizards there are 
labial glands, opening at the bases of the teeth, and an intermaxil- 
lary or internasal gland in the septum between the nasal cavities, as 
well as palatal glands near the choanz (the internasal gland is lacking 
