436 ELEMENTARY ANATOMY. [LESS. 



the single exception of the Crocodiles, in which a transverse 

 fold, or soft palate, hangs down in front of the posterior nares. 

 A distinct uvula is only found in certain members of man's 

 own order. The soft palate, however, may attain a greater 

 development than it does in man, as e.g. in the Cetacea, 

 where it is changed into a muscular canal, which prolongs 

 the posterior nares, downwards and backwards. We may 

 find, as in the Camel, a second and very long transverse pro- 

 cess hanging down from the palate, just in front of the true 

 velum. It ordinarily hangs down the throat, but in males at 

 the rutting season is protruded from the mouth in a singular 

 and conspicuous manner. 



The soft palate may extend eight inches beyond the hard 

 palate, and indeed half-way down the neck, as in the Ant- 

 eater. 



The hard palate, instead of only having very slight trans- 

 verse prominences, as in man, may have them produced into 

 strongly projecting ridges, as in the Pig, or into transverse 

 rows of conical horny spines, as in the Echidna, or into great 

 depending and dentated ridges, as in the Giraffe a greater 

 extension of a similar structure constitutes the baleen-bearing 

 ridges of the Whalebone Whales. 



The situation of the opening of the posterior nares has 

 already been indicated in the Lesson on the Skull. The 

 Eustachian tubes and teeth have also been already noticed. 



The cheeks may be distensible, so as to form pockets, or 

 " cheek-pouch js," as in the Ornithorhynchus. some Rodents, 

 and even in man's own order, as e.g. in the Baboons and the 

 smaller and commoner Monkeys of Africa and Asia. 



That median opening of the windpipe which exists in man, 

 exists also in all air-breathing Vertebrates even those which, 

 like Mcnobranckus, have at the same time permanent gills. 

 No such structure exists, however, in Fishes, 1 although in 

 the Lamprey we meet with something analogous, as in that 

 animal a canal conveying water to the gills opens at the 

 back of the mouth, on the ventral aspect of the opening of the 

 gullet. In ths higher Fishes, instead of one such opening, 

 several on each side serve (as we shall see in the Twelfth 

 Lesson) to convey water from the alimentary tract to the 

 respiratory organs. 



4. The spittle, or SALIVARY, GLANDS of man are three in 

 number : (i) The parotid glands, one of which lies on each 



1 As to the ductus pneumaticus of the swim-bladder, see Lesson XI T 6 i 

 p. 465. 



