. A manual of zoology. Zoology. 538 CHORD ATA. tions with aquatic life; hence the idea of a 'sixth sense,' hxcking to man [cf. j). 125). The end buds are especially collected in the neighborhood of the mouth, on the lips and bar- bels. Since they also occur in the mucous membrane of the mouth, especially in the palatal regions, they connect with the taste organs. The taste buds have the same structure as the end buds of fishes. They occur in all classes of vertebrates, and are most abundant in man in the walls of the circumvallate papillje at the base of the tongue; in rodents on t
. A manual of zoology. Zoology. 538 CHORD ATA. tions with aquatic life; hence the idea of a 'sixth sense,' hxcking to man [cf. j). 125). The end buds are especially collected in the neighborhood of the mouth, on the lips and bar- bels. Since they also occur in the mucous membrane of the mouth, especially in the palatal regions, they connect with the taste organs. The taste buds have the same structure as the end buds of fishes. They occur in all classes of vertebrates, and are most abundant in man in the walls of the circumvallate papillje at the base of the tongue; in rodents on the large foliate papillae, etc. The end buds also lead to the olfactory organs. The olfactory eiiithelium of many fishes and amphibia is a stratified epithelium with closely arranged end buds (fig. 572), By disappearance of. Fig. 572.—Section of olfactory epithelmm of a fish (Belone). (From O. Hertwig, after Blaue.) e, epitlleliuni; k. olfactory buds ; ?i, nerves. the isolating parts of the ordinary epithelium the end buds form a continuous sensory epithelium, which is the rule in most ver- tebrates. The olfactory organ, the nose, lined with its sensory epithelium, acquires a special interest both from its grade of development and from the imi)ortant systematic distinctions it affords. Except the cyclostomes, which have an unpaired nasal sac, all vertebrates have paired olfactory organs. In adult fishes and in the embryos of higher forms are two jjits which lie in front of or dorsal to the mouth; they are either distinct from it or only connected with it by an oronasal groove in the skin (fig. 50'J). If the animal be terrestrial and replace branchial by pulmonary respiration, a respiratory canal is developed in connexion with the nose. The oronasal groove closes to a tube which begins with an o^Jeuing (nostril) on the surface and ends with a second opening (choana) in the mouth cavity. The olfactory sac prop(!r is included in the wall of this tube, usually on its dorsal surfa
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