. Text book of zoology. Zoology. 11. Organs. 5. Sense Onjan.'i. 19. tlie tip, and continued at the other end into a nerve fibre, which passes to the front part of the brain. Amongst Insects, which have been proved by many experiments to possess a very acute sense of smell, the olfactory organs are situated upon the antennae. These are provided with delicate hairs, which, like arthropod hairs in general, are evaginations of the cuticle; they are very thin walled, generally seated in small depressions, and into each, a thread-like process extends from one or more underlying sense cells (Fig. 18)
. Text book of zoology. Zoology. 11. Organs. 5. Sense Onjan.'i. 19. tlie tip, and continued at the other end into a nerve fibre, which passes to the front part of the brain. Amongst Insects, which have been proved by many experiments to possess a very acute sense of smell, the olfactory organs are situated upon the antennae. These are provided with delicate hairs, which, like arthropod hairs in general, are evaginations of the cuticle; they are very thin walled, generally seated in small depressions, and into each, a thread-like process extends from one or more underlying sense cells (Fig. 18). Whilst these insectan structiu'es are probably true olfactory organs, there are mimerous contrivances to which, even in this book, the same name is applied, but â with doubtful right. This is the case with aU the " olfactory organs" of aquatic animals, which seldom or never come in contact with air. The olfactory pits of Fish, which, from their position, &c., are homologous* with the olfactoiy organs of higher Vertebrates, can, for instance, hardly be really olfactory. This is also tnae of the delicate " olfactory hairs " present on the antennules of many Crustacea; like the above-mentioned structures in Pish they are undoubtedly sense organs, but their special function is unknown: they are, perhaps, organs of taste. Gustatory Organs are affected only by substances which occur in a liquid form. In the Vertebrata they are represented by the so-called taste-buds of the tongue and the walls of the mouth, specially modified tracts of the buccal epithelium, consisting of groups of cells, amongst which are long thin cells with a delicate point projecting from the free end; these are, probably, the true organs of taste. The buds are supplied with nerve fibres which branch between the cells. In Fish, taste-buds may occur on the external surface of the body; similar structures are found also in many Chsetopods and Molluscs {, Gastropods), not only in the b
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
