316 



AVES. 



bands from the lower and internal edge of the 

 lower jaw ; these unite and surround the cerato- 

 hyals or cornua of the os hyoides ; and as they 

 draw forward the os hyoides, protrude the 

 tongue from the beak. 



4th. The Cerato-liyoideus passes from the 

 cerato-hyal to the uro-hyal, and is therefore 

 subservient to the lateral movements of the 

 tongue. 



5th. The Sterno-hyoidd are replaced by a 

 slip of muscle which extends from the anterior 

 surface of the upper larynx to be attached to 

 the base of the glosso-hyal. 



6th. A small and short muscle is single or 

 azygos ; it passes from the basi-hyal to the 

 under part of the glosso-hyal ; it depresses the 

 tip of the tongue and elevates its base. 



7th. A short muscle which arises from the 

 junction of the basi-hyal with the cerato- and 

 uro-hyals, and is inserted into the upper and 

 outer angle of the base of the glosso-hyal. 



All these muscles are remarkably large in 

 the Woodpecker, in which there is a singular 

 pair of muscles that may be termed Cerato- 

 tracheales, (h, fig. 154.) They arise from the 

 trachea about eight lines from the upper larynx, 

 twist four,times spirally round the trachea, and 

 then pass forward to be inserted into the base 

 of the cerato-hyals. This is the principal re- 

 tractor of the singular tongue in this species. 



Salivary glands. The salivary organs, being 

 in general developed in a degree corresponding 

 to the extent of the changes which the food 

 undergoes in the mouth, and the length of 

 time during which it is there detained, are by 

 no means so conspicuous a part of the diges- 

 tive system in Birds as in Mammals. Glands 

 which pour out their secretion upon the food 

 prior to deglutition are, however, met with in 

 every bird, but vary in number, position, arid 

 complexity of structure. 



In some species, as the Crow, they are of 

 the simplest structure, consisting of a series 

 of unbranched, cone-shaped follicles or tubules, 

 opening separately upon the mucous mem- 

 brane of the mouth, along the sides of which 

 cavity they are situated. They pour out a 

 viscid mucus, and are the only traces of a 

 salivary system met with in this bird. 



In many other birds, and especially in the 

 Scratching, Wading, and Swimming Orders, 

 glands of the conglomerate structure are found 

 beneath the lower jaw, analogous to the sub- 

 maxillary glands of quadrupeds. 



In the Goose they occupy the whole of the 

 anterior part of the space included by the rami 

 of the lower jaw, being of an elongated form, 

 flattened and closely united together at the 

 middle line. On either side of this line the mu- 

 cous membrane of the mouth presents inter- 

 nally a series of pores, each of which is the 

 terminal orifice of a distinct gland or aggre- 

 gate of ramified ducts. 



A third and higher form of salivary gland, 

 in which the secretion of the conglomerate 

 mass is conveyed into the mouth by a single 

 duct, is found in the Woodpeckers and some 

 species of the Rapacious Order. In the latter 

 birds these glands are termed, from their situ- 



Fig. 154 



Tongue and salivary glands, Woodpecker. 

 ation, anterior palatine : in the Pica they 

 correspond to the parotid and sublingual of 

 Quadrupeds. 



The sublingual glands of the Woodpecker 

 are of extraordinary size, extending from the 

 angle to the symphysis of the lower jaw. The 

 single ducts of each gland unite just before 

 their termination, which is a simple orifice at 

 the apex of the mouth. The structure of these 

 glands is shown at i, k, fg. 154. 



Besides the preceding, which may be con- 

 sidered as the true salivary glands, there are 

 numerous accessory follicles in different parts 

 of the oral apparatus of birds. In the Water- 

 hen (GaUinula chloropus) there is a series of 

 ccecal glandular tubes along each side of the 

 tongue ; and it is interesting to note that glan- 



