740 COMPARATIVE ANATOMY 



is added a large glandular part which develops between that portion 

 called the copula or medial region and the lower body. The amphibian 

 tongue secretes slime which is rather useful in capturing its prey. In 

 the anura the tongue is fastened to the margin of the jaw, while its free 

 end when not in use lies on the floor of the mouth. In urodeles a much 

 greater portion of the tongue is attached than in anura, where not only 

 the anterior margin of the tongue, but a part of the ventral surface as 

 well, is held quite definitely in place by attachments. 



The supporting skeleton of the tongue, as mentioned above, usually 

 consists of two pairs of horns largely formed from the ventral ends of 

 the hyoid and first branchial arches. The median portion or body which 

 unites these horns is known as the copula. The reptilian tongue includes 

 the parts already mentioned which are found in the amphibia, and in ad- 

 dition a median growth which arises between the basi-hyal and the lower 

 jaw known as the tuberculum impar (Fig. 432, t). Added to this, there 

 is found a pair of lateral folds lying above the first visceral (mandibular) 

 arch. From now on, as these parts develop, the trigeminal nerve sends 

 twigs to the tongue in addition to the hypoglossal and glossopharyngeal 

 as in the lower groups. In turtles and crocodiles, the tongue lies on the 

 floor of the mouth and cannot be protruded. In reptiles possessing a 

 retractile tongue, the hyoid apparatus extends into that organ. The un- 

 paired cephalad portion which we have called the os entoglossum is 

 equivalent to the term copula or basi-hyal; the retractor muscles are 

 usually attached to the two horns. In the tongues of birds, the lateral 

 parts of the reptilian tongue are not to be found and consequently there 

 is no branch from the trigeminal nerve. It is to be remembered that 

 during the development of a part, the nerves follow the growing muscle. 

 The bird's tongue has no intrinsic muscles. It has many varieties of 

 form, but is usually slender and covered with horny papillae. Even its 

 skeleton is reduced, there being only an os entoglossum with a pair of 

 structural elements attached in front, known as the paraglossae, while, 

 on the sides, a pair of horns form the first branchial arch, and, in the 

 median line behind, there is a portion called the urohyal. This is well 

 marked in the woodpecker, as has been stated. 



Now, as to the use of the tongue. With the exception of the whale 

 the tongue is very mobile in all forms of mammalian life. The mobility 

 reaches its extreme in the ant-eaters (Fig. 387). It is largely due to the 

 intrinsic muscles which have been derived to a considerable extent from 

 the hypo-branchial musculature. The tongue itself is developed from 

 the unpaired elevation the tuberculum impar, and from two thickenings 

 on the mandibular arch, which, together with the fleshy ridges above the 

 hyoid arch, form the tongue. These fleshy ridges above the hyoid arch 

 form the back part of the tongue. The line formed between the anterior 

 and posterior parts cannot very readily be seen in the adult, but it is quite 

 close to the circumvallate papillae and the foramen caecum. This latter 



