THE ORGANS OF SMELL. 381 



must be seated in the palate and fauces. Others possess a large tongue, which 

 presents prehensile teeth rather than sensory papillse. 



A sense of taste, or, at all events, a power of discriminating proper food, 

 would seem to be present in m^st, if not all, of the non-vertebrate animals, even 

 in the Infusoria, many of which appear to exercise a faculty of selection in re- 

 gard to their food. The seat of this sense is probably here too in the neighbor- 

 hood of the entrance of the digestive apparatus ; but Its proper organ or organs 

 are unknown. The so-called tongue of the Cephalopods, and the odontophore 

 of the Gasteropods, are rather accessory digestive than gustatory organs. The 

 larvse of insects, the feeding propensities of which are so strong and peculiar, 

 nevertheless present no special organ of taste. 



THE SENSE OF SMELL. 



The Organs of Smell. 



The nasal cavities, or nasal fossce, situated between the base of the 

 cranium and the roof of the mouth, at the upper and fore part of the 

 face are the seats of the organs concerned in the sense of smell. The 

 roof, sides and floor of these cavities are formed by the surrounding 

 bones of the cranium and face, see Fig. 72. The ethmoid bone, which 

 forms part of the floor of the cranial cavity, is, however, the most im- 

 mediately concerned in the formation of the olfactory part of the nasal 

 fossae ; its cribriform plates, Fig. 72, enter into the formation of the 

 roof; its cellular lateral portions, 3, constitute the convoluted sides of 

 the upper part of the cavity ; Avhilst its median septum, 4, assists in form- 

 ing the partition which divides one nasal fossa from the other. The 

 fore part of the fossae is completed, at the sides and in the median line, 

 by the nasal cartilages, Fig. 71, 4, which are adapted to the margin 



Fig. 71. 



Fig. 71. Lateral view of the bones and cartilages of the nose. 1, left nasal bone. 2, ascending part of the 

 superior maxillary bone. 3, lachrymal groove for the lodgment of the lachrymal ac. 4, cartilages of the 

 side, and alee of the nose. (Arnold.) 



of the great nasal aperture seen in the bones, as well as to the bony 

 septum. These cartilages give form and stiffness to the visible part 

 of the nose ; they are provided with certain small subcutaneous mus- 

 cles. The nasal fossae open anteriorly by the apertures called the an- 

 terior nares, or nostrils, which are provided with short hairs, or vibrissce, 

 to prevent the introduction of coarse foreign bodies. Behind, the fossae 

 open, by two orifices called the posterior nares, into the upper part of 



