THE TONGUES OF BIRDS. 1005 



to do not only to some extent with the shape of the tongue, but on 

 them depends the power of movement, of extending and retracting the 

 tongue, and the ability to suck up the nectar of flowers. These little 

 bones (fig. 1 a), when all are present, are eight in number, the three 

 foremost corresponding to the hyoid, the five hindmost to the first gill 

 arch, of a fish. The shape of these may vary somewhat, the proportions 

 much more, but, after all, the differences between them are not very 

 great. Tlie tongue is attached principally to the two foremost bones, 

 while the others are maiidy concerned with the motions of the tongue, 

 furnishing attachment for the muscles by which it is protruded and 

 retracted, as well as serving as guides to make the apparatus run true. 

 The varying proportions of the bones tell something of the importance 

 of the tongue and something of its use. If the foremost bones tire 

 well developed, then the .tongue is thick and fleshy, as in the duck, 

 and has considerable to do in obtaining or manipulating food (fig. 1 c). 

 If the foremost bones are small, or are represented by cartilage, then 

 the tongue plays an insignificant part, as in the cassowary, or is a mere 

 rudiment, as in the cormorant and pelican (fig. 1 h). If the hindmost 

 bones are long, the tongue is protruded in getting food, and the length 

 of these bones is a direct measure of the extent to which the tongue 

 can be extendea. The proportions of the intermediate bones, the 

 ceratobranchials, have to do with the length of the bill. 



The hyoid probably has a more direct relation to the tongue in birds 

 than in any other group of vertebrates. Among mammals the most 

 important office of the hyoid is to support the larynx, and this duty it 

 often performs very effectively. In reptiles the hyoid has much to do 

 with breathing, and in turtles, whose ribs are so tied up as to be of no 

 use in respiration, the hyoid may be seen working backward and for- 

 ward, forcing air into the lungs. The hyoid of frogs is mostly orna- 

 mental, being a hint that the tadpole had an elaborate and well- 

 developed system of gills, which was put off' together with the tail. In 

 fishes the hyoid forms a firm support to the gill arches, although it also 

 supports the tongue. In birds the two ceratohyals, or glossohyals, as 

 they are sometimes called from their intimate connection with the 

 tongue, are embedded in the tongue and usually terminate in cartilages 

 which are prolonged for some distance forward well toward the tip 

 of the tongue. Their posterior portions end in the main posterior 

 points of the tongue (fig. 1 a). 



There is an intimate relation between the dermis and the epidermal 

 layer of the tongue, and if a thin tongue is held \\\) to the light, the little 

 blood vessels may be readily seen running into the harder portion. At 

 the same time, if a tongue is allowed to macerate for a little, the con- 

 nection between the dermis and epidermis is easily broken down and 

 the horny external layer may be slipped off as a glove is drawn from 

 a finger. 



A very curious thing happens in the titmice — to be exact, this is 



